Alkaline subcritical water compositions, aqueous compositions, devices and containers

Abstract

The purpose of the present invention is to provide an alkaline subcritical water composition, a water-containing composition, a device, and a container which are capable of inhibiting corrosion of a reaction device and capable of decomposing a polymer and the like. The present disclosure is an alkaline subcritical water composition having a pH of 13.7 or less and a potential of 400 mV or more when a current density exceeds 10 mA / cm2 in an anodic polarization curve in which a steel material is used in a test electrode.

Description

Technical Field

[0001] This disclosure relates to alkaline subcritical water compositions, aqueous compositions, apparatus, and containers. Background Technology

[0002] In light of the current necessity of environmental protection and the construction of a resource-recycling society, various studies have been conducted on the reuse of organic materials such as plastics. Among these studies, subcritical water decomposition technology has been employed. For example, Patent Document 1 and Non-Patent Document 1 describe methods for decomposing fluoropolymers by reacting them in subcritical water containing alkaline compounds such as potassium hydroxide.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-155478

[0006] Non-patent literature

[0007] Non-patent literature 1: Jin Hamaura et al., Eur. Polym. J. 182 (2023), 111724 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The purpose of this disclosure is to provide an alkaline subcritical water composition, an aqueous composition, an apparatus, and a container capable of inhibiting corrosion of reaction equipment and decomposing polymers, etc.

[0010] Methods for solving problems

[0011] This disclosure (1) relates to an alkaline subcritical water composition having a pH below 13.7, and a current density exceeding 10 mA / cm² in an anodic polarization curve using steel as a test electrode. 2 The potential at that time is above 400mV.

[0012] This disclosure (2) relates to the alkaline subcritical water composition of this disclosure (1), which is above 180°C and below 250°C.

[0013] This disclosure (3) relates to the alkaline subcritical water composition of disclosure (1) or (2), wherein the steel contains 8% by mass or more Ni.

[0014] This disclosure (4) relates to an alkaline subcritical water composition in any combination with any of the present disclosures (1) to (3), having a pH of 13 or more and 13.5 or less, a temperature of 200°C or more and 235°C or less, wherein the steel contains 15% by mass or more of Ni and 10% by mass or more of Cr.

[0015] This disclosure (5) also relates to an aqueous composition having a temperature above 180°C and below 250°C, and a current density exceeding 10 mA / cm² in an anodic polarization curve using steel as a test electrode. 2 The potential at that time is above 400mV and below 900mV.

[0016] This disclosure (6) relates to an aqueous composition of this disclosure (5), wherein the steel contains 8% by mass or more Ni.

[0017] This disclosure (7) relates to an aqueous composition of disclosure (5) or (6) having a pH of 10 or higher and 13.7 or lower.

[0018] This disclosure (8) relates to an aqueous composition in any combination with any of the present disclosures (5) to (7), having a pH of 13 or more and 13.5 or less, a temperature of 200°C or more and 235°C or less, wherein the steel contains 15% by mass or more of Ni and 10% by mass or more of Cr.

[0019] This disclosure (9) relates to an apparatus comprising an alkaline subcritical water composition of any combination of any one of the present disclosures (1) to (4) or an aqueous composition of any combination of any one of the present disclosures (5) to (8).

[0020] This disclosure (10) relates to a container having an alkaline subcritical water composition of any combination of any one of the present disclosures (1) to (4) or an aqueous composition of any combination of any one of the present disclosures (5) to (8).

[0021] Invention Effects

[0022] According to this disclosure, it is possible to provide alkaline subcritical water compositions, aqueous compositions, apparatuses, and containers that can inhibit corrosion of reaction devices and decompose polymers, etc. Detailed Implementation

[0023] The following details this disclosure.

[0024] This disclosure relates to an alkaline subcritical water composition having a pH below 13.7, and exhibiting a current density exceeding 10 mA / cm² in the anodic polarization curve using steel as the test electrode. 2 The potential at that time is 400mV or higher. The alkaline subcritical water composition disclosed herein has the above-described structure, thus it can suppress corrosion of the reaction apparatus and can be used for subcritical water treatment of various objects. For example, it can decompose polymers, etc.

[0025] The alkaline subcritical water composition disclosed herein comprises subcritical water. Subcritical water is water in a liquid state within a temperature range exceeding 100°C and below the critical temperature of 374°C obtained by pressurization. Subcritical water possesses physical properties different from water below 100°C, particularly in subcritical water in the range of 200°C to 300°C, where the relative permittivity decreases significantly, exhibiting lipid solubility substantially equivalent to methanol and acetone at room temperature, or 10 at room temperature. -14 The ion product of mol / L is 10. -11 The concentrations of hydrogen ions and hydroxide ions are on the order of mol / L, and are 30 times higher than those in water at room temperature. Therefore, it is known that subcritical water, particularly at temperatures between 200°C and 300°C, exhibits reactivity different from that of water at room temperature. The temperature of the alkaline subcritical water composition disclosed herein is preferably below 250°C, more preferably below 245°C, further preferably below 240°C, even more preferably below 235°C, and preferably above 180°C, more preferably above 200°C, even more preferably above 205°C, even more preferably above 210°C, particularly preferably above 215°C, particularly more preferably above 220°C, and especially more preferably above 225°C.

[0026] The water used in the preparation of subcritical water is not particularly limited; any type of water can be used, such as tap water, ion-exchanged water, distilled water, or well water. From the viewpoint of suppressing side reactions caused by the influence of coexisting salts, ion-exchanged water and distilled water are preferred. Regarding the amount of water used, it is sufficient to fully impregnate the object being treated. However, if very little water is introduced into the pressurized, sealed container, it will all turn into water vapor after heating and will not reach a subcritical water state; therefore, this must be considered.

[0027] The alkaline subcritical water composition disclosed herein preferably comprises at least one alkaline compound selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

[0028] Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide, with sodium hydroxide and / or potassium hydroxide being preferred. It is known that potassium hydroxide has higher activity and higher alkalinity in concentrated solutions compared to sodium hydroxide. From this perspective, potassium hydroxide can be considered the optimal choice.

[0029] Examples of alkaline earth metal hydroxides include calcium hydroxide and barium hydroxide.

[0030] The concentration of the alkaline compound in the above-mentioned alkaline 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, and even more preferably 0.35 M or less. It is also 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. It should be noted that, as is known to those skilled in the art, the unit "M" refers to mol / L.

[0031] The alkaline subcritical water composition disclosed herein exhibits a current density exceeding 10 mA / cm² in the anodic polarization curve using steel as the test electrode. 2 The potential at that time was above 400mV. In the anodic polarization curve using steel as the test electrode, the current density exceeded 10mA / cm. 2 The voltage at that time is preferably 450mV or higher, more preferably 500mV or higher, even more preferably 550mV or higher, and preferably 900mV or lower.

[0032] The above anodic polarization curves were measured using a potentiostat at a potential scan rate of 20 mV / min according to JIS G0577.

[0033] The aforementioned steel preferably includes at least one type selected from the group consisting of Ni, Cr, and Fe.

[0034] The aforementioned steel preferably contains 8% by mass or more Ni, more preferably 15% by mass or more Ni, and even more preferably 70% by mass or more Ni. There is no particular upper limit, but it is typically 90% by mass.

[0035] The steel mentioned above preferably contains 10% or more of Cr by mass, more preferably 20% or more of Cr by mass, and preferably 40% or less of Cr by mass, more preferably 30% or less of Cr by mass.

[0036] The steel preferably contains 5% by mass or more of Fe, more preferably 20% by mass or more of Fe, even more preferably 40% by mass or more of Fe, and preferably 80% by mass or less of Fe, more preferably 60% by mass or less of Fe, and even more preferably 50% by mass or less of Fe.

[0037] Examples of the aforementioned steels include SUS310S, SUS304L, and NCF600.

[0038] The alkaline subcritical water composition disclosed herein has a pH of 13.7 or less. Preferably, the pH of the alkaline subcritical water composition is 10 or more, more preferably 11 or more, even more preferably 12 or more, and still more preferably 13 or more. Furthermore, it is preferably 13.6 or less, and more preferably 13.5 or less.

[0039] This disclosure also relates to an aqueous composition having a temperature above 180°C and below 250°C, and a current density exceeding 10 mA / cm² in the anodic polarization curve of a test electrode made of steel. 2 The potential at that time is 400mV or more and 900mV or less. The aqueous composition disclosed herein has the above-described structure, thus it can suppress corrosion of the reaction apparatus and can be used for the treatment of various objects. For example, it can decompose polymers, etc.

[0040] The temperature of the aqueous composition disclosed herein is below 250°C, preferably below 245°C, more preferably below 240°C, even more preferably below 235°C, and also above 180°C, preferably above 200°C, more preferably above 205°C, even more preferably above 210°C, even more preferably above 215°C, particularly preferably above 220°C, and especially more preferably above 225°C.

[0041] The aqueous composition disclosed herein exhibits a current density exceeding 10 mA / cm² in the anodic polarization curve when steel is used as the test electrode. 2 The potential at that time was above 400mV and below 900mV. In the anodic polarization curves using steel as the test electrode, the current density exceeded 10mA / cm. 2 The potential at that time is preferably 450mV or higher, more preferably 500mV or higher, and even more preferably 550mV or higher.

[0042] In the aqueous compositions disclosed herein, the steels mentioned above can be the steels listed in the alkaline subcritical water compositions disclosed herein.

[0043] The aqueous compositions disclosed herein preferably contain subcritical water.

[0044] The aqueous composition disclosed herein preferably comprises at least one alkaline compound selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides. Substances listed in the alkaline subcritical water compositions of this disclosure can be used as the aforementioned alkali metal hydroxides and alkaline earth metal hydroxides.

[0045] The concentration of the alkaline compound in the aqueous composition disclosed herein can be set to the same range as the concentration described for the alkaline subcritical water composition of this disclosure.

[0046] The pH of the aqueous composition of the present invention is preferably 10 or higher, more preferably 11 or higher, even more preferably 12 or higher, even more preferably 13 or higher, and preferably 13.7 or lower, more preferably 13.6 or lower, and even more preferably 13.5 or lower.

[0047] The alkaline subcritical water composition and aqueous composition disclosed herein are preferably used in contact with the aforementioned steel. For example, they are more preferably used in contact with containers made of the aforementioned steel. In addition, they are also preferably used for the treatment of objects in containers made of the aforementioned steel (preferably subcritical water treatment). The alkaline subcritical water composition and aqueous composition disclosed herein do not easily corrode the steel even when in contact with the aforementioned steel.

[0048] The alkaline subcritical water composition and aqueous composition disclosed herein can be used for the treatment of various objects, and are preferably used for subcritical water treatment, suitable for the decomposition of polymers, etc.

[0049] 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] resin; polyphenylene ether [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); and polyphenylene sulfide [PPS], polyketone sulfide, polyetherimide, and polyimide [PI]. Furthermore, examples include fluoropolymers such as ethylene [Et] / TFE copolymer [ETFE], polyvinylidene fluoride [PVF], and polyvinylidene fluoride [PVdF]. The aforementioned nylon MXD6 is a crystalline condensation polymer obtained from m-xylenediamine [MXD] and adipic acid. From the viewpoint of easy depolymerization, condensation systems such as polyester resins and epoxy resins are preferred, with polyester resins being more preferred.

[0050] Alternatively, it can be an oligomer that constitutes a polymer, or a substance formed by adding functional groups to an oligomer.

[0051] By using the alkaline subcritical water composition and aqueous composition disclosed herein, the decomposition of the aforementioned polymers, etc., can be promoted.

[0052] Next, a method for reacting and decomposing the polymer in the alkaline subcritical water composition and aqueous composition disclosed herein will be described. For example, water, the polymer to be treated, and an alkaline compound as needed are added to a pressure vessel of a size corresponding to the amount of the polymer to be treated, and the pressure vessel is then pressurized and sealed. To pressurize the inside of the pressure vessel, a gas can be introduced. Examples of such a gas include air, argon, and nitrogen. The pressure level can be around 0.5 MPa, and there is no particular limitation.

[0053] The decomposition reaction is initiated by heating the pressure vessel that has undergone the above process. The alkaline subcritical water composition and aqueous composition of this disclosure can be generated within the pressure vessel during the above decomposition reaction. The heating temperature is below 250°C, preferably below 245°C, more preferably below 240°C, further preferably below 235°C, and also above 180°C, preferably above 200°C, more preferably above 205°C, further preferably above 210°C, even more preferably above 215°C, particularly preferably above 220°C, and especially preferably above 225°C. If the pressure vessel itself has a heating mechanism, heating can be performed using that mechanism; if the pressure vessel itself does not have a heating mechanism, the entire pressure vessel can be heated in an autoclave or oven. The reaction time can range from 1 minute to 100 hours, preferably from 1 minute to 1 hour, and more preferably from 1 to 30 minutes. The reaction pressure can range from 0.1 to 22 MPa.

[0054] The aqueous solution following the decomposition reaction contains monomers and hydrocarbon compounds that constitute the polymer. The decomposition method can include a recovery step after the decomposition process to reclaim the generated monomers and hydrocarbon compounds. By including this recovery step, the decomposition method enables efficient resource utilization.

[0055] Preferably, the above decomposition method includes a pulverizing step before the decomposition step, in which the polymer is pulverized into particles with a maximum linear length of 3 mm or less. By including the pulverizing step in the above decomposition method, the polymer can be easily decomposed.

[0056] There are no particular limitations on the pulverizing method; examples include cryogenic pulverizers, disc mills, hammer mills, mortar mills, and jet mills.

[0057] The pulverizing temperature is preferably above -200°C, and more preferably below 90°C. More preferably below 40°C, and even more preferably below 0°C.

[0058] The maximum linear length of the pulverized polymer particles is preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1 mm or less, and particularly more 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. If the average particle size of the pulverized polymer particles is within the above range, the polymer is more easily decomposed.

[0059] To determine the maximum straight line length, SEM images were used to observe more than 100 secondary particles, and the major and minor axes of each secondary particle were measured. The largest major and minor axis was taken as the maximum straight line length.

[0060] This disclosure also relates to an apparatus having the above-described alkaline subcritical water composition or the above-described aqueous composition.

[0061] The alkaline subcritical water composition and aqueous composition disclosed herein can suppress corrosion of the reaction apparatus and can be used for the treatment of various objects, preferably for subcritical water treatment. Therefore, the apparatus disclosed herein is suitable as an apparatus for subcritical water treatment. Furthermore, the alkaline subcritical water composition and aqueous composition disclosed herein can suppress corrosion of the reaction apparatus and can decompose polymers, etc., therefore, the apparatus disclosed herein is particularly suitable as an apparatus for the decomposition of polymers, etc.

[0062] The portions of the apparatus disclosed herein that come into contact with the aforementioned alkaline subcritical water composition and aqueous composition are preferably made of the aforementioned steel. The apparatus of this disclosure is also preferably equipped with the container described later in this disclosure.

[0063] This disclosure also relates to containers having the above-described alkaline subcritical water composition or the above-described aqueous composition.

[0064] The alkaline subcritical water composition and aqueous composition disclosed herein can inhibit corrosion of the reaction apparatus and can be used for the treatment of various objects, preferably for subcritical water treatment. Therefore, the container disclosed herein is suitable as a container for subcritical water treatment. Furthermore, the alkaline subcritical water composition and aqueous composition disclosed herein can inhibit corrosion of the reaction apparatus and can decompose polymers, etc., therefore, the container disclosed herein is particularly suitable as a container for the decomposition of polymers, etc.

[0065] The container disclosed herein is preferably made of the aforementioned steel.

[0066] The above describes the implementation methods, but it is understood that various changes in form and detail may be made without departing from the spirit and scope of the claims.

[0067] Example

[0068] The present disclosure will now be described with reference to specific embodiments, but the present disclosure is not limited to these embodiments.

[0069] The values ​​in the examples were measured using the following methods.

[0070] (1) Determination of corrosion initiation potential

[0071] The anodic polarization curve was determined according to JIS G0577. A current density of 10 mA / cm² was achieved using an electrokinetic potentiostat, starting from the spontaneous potential and scanning at a potential scan rate of 20 mV / min. 2 The potential at that time is taken as the corrosion initiation potential.

[0072] (Example 1)

[0073] The test electrode used was NCF600 (Ni: ≥72.00 wt%, Cr: 14.00–17.00 wt%, Fe: 6.00–10.00 wt%). A potassium hydroxide aqueous solution with pH adjusted to 13.5 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. A potentiostat was used to increase the voltage at a potential scan rate of 20 mV / min to confirm that the current density exceeded 10 mA / cm². 2 The potential at that time. The results are shown in Table 1.

[0074] (Example 2)

[0075] The experimental electrode used was an NCF600. A potassium hydroxide aqueous solution with a pH adjusted to 13 was placed in the container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. A potentiostat was used to increase the voltage at a potential scan rate of 20 mV / min to confirm that the current density exceeded 10 mA / cm². 2 The potential at that time. The results are shown in Table 1.

[0076] (Example 3)

[0077] The test electrode used was SUS310S (Ni: 19.00–22.00% by mass, Cr: 24.00–26.00% by mass). A potassium hydroxide aqueous solution with a pH adjusted to 13 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 200°C. A potentiostat was used to increase the voltage at a potential scan rate of 20 mV / min, confirming that the current density exceeded 10 mA / cm². 2 The potential at that time. The results are shown in Table 1.

[0078] (Example 4)

[0079] The experimental electrode used was a SUS310S. A potassium hydroxide aqueous solution with a pH adjusted to 13.3 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 200°C. A potentiostat was used to increase the voltage at a potential scan rate of 20 mV / min to confirm that the current density exceeded 10 mA / cm². 2 The potential at that time. The results are shown in Table 1.

[0080] (Example 5)

[0081] The experimental electrode used was a SUS310S. A potassium hydroxide aqueous solution with a pH adjusted to 13 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. A potentiostat was used to increase the voltage at a potential scan rate of 20 mV / min to confirm that the current density exceeded 10 mA / cm². 2 The potential at that time. The results are shown in Table 1.

[0082] (Comparative Example 1)

[0083] The experimental electrode used was an NCF600. A potassium hydroxide aqueous solution with a pH adjusted to 14 was placed in the container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. A potentiostat was used to increase the voltage at a potential scan rate of 20 mV / min to confirm that the current density exceeded 10 mA / cm². 2 The potential at that time. The results are shown in Table 1.

[0084] (Comparative Example 2)

[0085] The experimental electrode used was an NCF600. A potassium hydroxide aqueous solution with a pH adjusted to 14 was placed in the container, pressurized to 0.8 MPa with argon gas, and then heated to 250°C. A potentiostat was used to increase the voltage at a potential scan rate of 20 mV / min to confirm that the current density exceeded 10 mA / cm². 2 The potential at that time. The results are shown in Table 1.

[0086] (Comparative Example 3)

[0087] The test electrode used was an NCF600. Pure water was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 200°C. A potentiostat was used to increase the voltage at a potential scan rate of 20 mV / min, confirming that the current density exceeded 10 mA / cm². 2 The potential at that time. The results are shown in Table 1.

[0088] Table 1

[0089] (Example 6)

[0090] 100 mg of PET film (manufactured by Toray Industries, Inc., "Lumirror Film") and 20 ml of potassium hydroxide aqueous solution with pH adjusted to 13.5 were placed in the inner cylinder, and the inner cylinder and the container were then placed into 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. The reaction was allowed to proceed for 1 minute after the internal temperature of the pressure vessel reached 230°C. The reaction pressure was set to 2.8 MPa. After the reaction was completed, the electric furnace was stopped, the pressure vessel was removed from the furnace, and cooled by forced air. The remaining film was recovered, washed with pure water, dried, and its weight was measured to calculate the residual amount. The results are shown in Table 2.

[0091] It should be noted that the composition of Example 6 has the same pH, temperature and composition as the composition of Example 1, and therefore the corrosion potential is also the same.

[0092] (Examples 7-9, Comparative Example 4)

[0093] In Example 6, instead of an aqueous potassium hydroxide solution with a pH of 13.5, an aqueous potassium hydroxide solution or pure water with a pH as described in Table 2 was used. The reaction temperature, reaction pressure, and reaction time were changed as described in Table 2. Otherwise, the reaction was carried out in the same manner as in Example 6, and the residual amount of the membrane was calculated. The results are shown in Table 2.

[0094] It should be noted that the composition of Example 7 has the same pH, temperature, and composition as the composition of Example 2, the composition of Example 8, the composition of Example 3, and the composition of Example 9, and the composition of Example 4, and therefore the corrosion potential is also the same.

[0095] Table 2

Claims

1. An alkaline subcritical water composition having a pH below 13.7, In the anodic polarization curves using steel as the test electrode, the current density exceeds 10 mA / cm². 2 The potential at that time is above 400mV.

2. The alkaline subcritical water composition according to claim 1, wherein the temperature is above 180°C and below 250°C.

3. The alkaline subcritical water composition according to claim 1 or 2, wherein, The steel contains more than 8% by mass of Ni.

4. The alkaline subcritical water composition according to any one of claims 1 to 3, wherein the pH is 13 or higher and 13.5 or lower. It is between 200℃ and 235℃. The steel contains more than 15% by mass of Ni and more than 10% by mass of Cr.

5. An aqueous composition having a temperature above 180°C and below 250°C, and exhibiting a current density exceeding 10 mA / cm² in an anodic polarization curve using steel as a test electrode. 2 The potential at that time is above 400mV and below 900mV.

6. The aqueous composition according to claim 5, wherein, The steel contains more than 8% by mass of Ni.

7. The aqueous composition according to claim 5 or 6, wherein the pH is 10 or higher and 13.7 or lower.

8. The aqueous composition according to any one of claims 5 to 7, wherein the pH is 13 or higher and 13.5 or lower. It is between 200℃ and 235℃. The steel contains more than 15% by mass of Ni and more than 10% by mass of Cr.

9. An apparatus comprising the alkaline subcritical water composition of any one of claims 1 to 4 or the aqueous composition of any one of claims 5 to 8.

10. A container comprising the alkaline subcritical water composition of any one of claims 1 to 4 or the aqueous composition of any one of claims 5 to 8.

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