Method for manufacturing aromatic compound having one phenolic hydroxyl group

Abstract

To provide a method for manufacturing an aromatic compound having one phenolic hydroxyl group by directly oxidizing an aromatic compound.SOLUTION: A method for manufacturing an aromatic compound having one phenolic hydroxyl group includes a hydroxyl group introduction step of introducing a phenolic hydroxyl group into the aromatic compound by bringing the aromatic compound into contact with plasma-treated water.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing an aromatic compound having one phenolic hydroxyl group.

Background Art

[0002] An aromatic compound into which one phenolic hydroxyl group is introduced has chemical and physical properties different from those of the original aromatic compound, and often can be used for new applications. For example, phenol obtained by introducing one phenolic hydroxyl group into benzene can be used as a disinfectant, a raw material for synthetic resins, and the like.

[0003] As a method for producing phenol, the cumene process using benzene and propylene as raw materials is widely used industrially. The cumene process is an indirect synthesis method that requires three chemical reaction steps: a step of producing cumene by adding benzene and propylene through a Friedel-Crafts reaction, a step of oxidizing cumene to produce cumene hydroperoxide, and a step of producing acetone and phenol by rearranging cumene hydroperoxide with an acid.

[0004] This cumene process has problems such as a large number of steps and the inevitable production of acetone as a by-product. To solve this problem, a method for producing phenol by direct oxidation of benzene has been studied. For example, Non-Patent Document 1 proposes a method for directly oxidizing benzene to synthesize phenol using 3-cyano-1-methylquinolinium ion as a photocatalyst.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, 3-cyano-1-methylquinolinium ion is a compound that is difficult to produce, and it is difficult to apply the method described in Non-Patent Document 1 to the production of an aromatic compound having one phenolic hydroxyl group that is practical. For this reason, there is a demand for a method for producing an aromatic compound having one phenolic hydroxyl group by direct oxidation of an aromatic compound without using a compound that is difficult to produce.

[0007] In view of the above circumstances, an object of the present invention is to provide a method for producing an aromatic compound having one phenolic hydroxyl group by directly oxidizing an aromatic compound.

Means for Solving the Problems

[0008] The present disclosure provides, for example, a method for producing an aromatic compound having one phenolic hydroxyl group described in [1] to [4] below. [1] A method for producing an aromatic compound having one phenolic hydroxyl group, comprising a hydroxyl group introduction step of introducing a phenolic hydroxyl group into the aromatic compound by bringing the aromatic compound into contact with plasma-treated water. [2] The aromatic compound is benzene, The method for production according to [1], wherein the aromatic compound having one phenolic hydroxyl group is phenol. [3] The manufacturing method according to [1] or [2], further comprising a plasma-treated water production step of forming bubbles by injecting air into an aqueous medium before the hydroxyl group introduction step, and generating the plasma-treated water by discharging electricity in the bubbles. [4] The manufacturing method according to any one of [1] to [3], wherein the pH of the plasma-treated water is 1 to 4.8.

Effects of the Invention

[0009] According to the present invention, a method for directly oxidizing an aromatic compound to produce an aromatic compound having one phenolic hydroxyl group can be provided.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. When a numerical range is indicated as X to Y, it means X or more and Y or less. For example, "5 to 100 nm" means 5 nm or more and 100 nm or less. Also, the materials, components, or methods exemplified in this specification can be used alone or in combination of two or more unless otherwise specified. In the following embodiments, "air" may be replaced with "a gas containing oxygen and nitrogen".

[0012] A method for producing an aromatic compound having one phenolic hydroxyl group according to this embodiment includes a hydroxyl group introduction step of introducing a phenolic hydroxyl group into the aromatic compound by bringing the aromatic compound into contact with plasma-treated water. In the hydroxyl group introduction step, the aromatic compound is directly oxidized by contacting with the plasma-treated water, and one phenolic hydroxyl group is introduced.

[0013] The above production method may further include a plasma-treated water generation step of generating plasma-treated water.

[0014] Although the reason why an aromatic compound having one phenolic hydroxyl group can be produced by the above production method is not necessarily clear, the present inventors presume that active species such as active nitrogen species and active oxygen species contained in the plasma-treated water oxidize the aromatic compound, thereby introducing one phenolic hydroxyl group into the aromatic compound to produce an aromatic compound having one phenolic hydroxyl group. The present inventors presume that among the active species contained in the plasma-treated water, peroxynitrous acid that can be generated by the reaction of nitrite ions and hydrogen peroxide in particular contributes to the oxidation of the above aromatic compound.

[0015] As used herein, "plasma" refers to a state of a substance that is electrically neutral as a whole and contains cations and electrons generated by the ionization of atoms or molecules. Plasma can be generated by applying energy to a gas through discharge, microwave irradiation, or the like. For example, when energy is applied to air, plasma of the air is generated, and when energy is applied to a noble gas, plasma of the noble gas is generated. The plasma of air contains active species such as active nitrogen species and active oxygen species. The plasma of a noble gas itself does not contain active species, but generates active species such as active nitrogen species and active oxygen species by reacting with air or the like. Plasma is roughly classified into low-temperature plasma in which cations and neutral particles are at a lower temperature than electrons, and thermal plasma in which the temperatures of cations and neutral particles are comparable to those of electrons, and low-temperature plasma is preferred.

[0016] As used herein, "plasma-treated water" is a concept that includes both an aqueous medium contacted with plasma of air and an aqueous medium contacted with active species generated by the reaction of plasma with air. Plasma-treated water contains active species such as active nitrogen species and active oxygen species.

[0017] 〔Plasma-treated water generation step〕 In the plasma-treated water generation step, plasma-treated water is generated by subjecting an aqueous medium to plasma treatment.

[0018] Examples of the aqueous medium include purified water such as distilled water and ion-exchanged water. The aqueous medium may contain salts such as sodium chloride and pH adjusters such as nitric acid. When the aqueous medium contains a salt, the content of the salt in the aqueous medium may be 0.1 to 100 mmol / L, and is preferably 5 to 30 mmol / L from the viewpoint of facilitating stable generation of plasma.

[0019] Examples of the method for subjecting an aqueous medium to plasma treatment include a method of bringing plasma of air into contact with the aqueous medium (Method 1), a method of reacting plasma of a noble gas such as helium with air and bringing these reaction products into contact with the aqueous medium (Method 2), and the like.

[0020] In Method 1, active species such as active nitrogen species and active oxygen species are generated in the aqueous medium by contacting the plasma of air with the aqueous medium. In Method 2, active species such as active nitrogen species and active oxygen species are generated in the aqueous medium by contacting the reactant with the aqueous medium.

[0021] As Method 1, it is preferable to form bubbles by injecting air into the aqueous medium and discharge electricity in the bubbles (Method 1-1). Thus, by discharging electricity in the bubbles, the air forming the bubbles can be made into plasma, and the plasma can be brought into contact with the aqueous medium to generate plasma-treated water. The plasma-treated water generated as described above may contain high-concentration active species such as active nitrogen species and active oxygen species.

[0022] In Method 1, it is preferable that the plasma-treated water contains active species such as nitrite ions and hydrogen peroxide. The content of nitrite ions in the plasma-treated water may be 0.1 to 5 mmol / L, or may be 0.2 to 2 mmol / L. The content of nitrite ions in the plasma-treated water may be 0.1 to 15 mmol / L, or may be 0.5 to 5 mmol / L. The contents of nitrite ions and hydrogen peroxide can be determined by a patch test such as a digital pack test. Specifically, the patch test may be performed by the method described in the examples.

[0023] In Method 1-1, the pH of the aqueous medium may be 1 to 8, or may be 1 to 5. From the viewpoint of facilitating the generation of active species such as peroxynitrous acid, it is preferably 1 to 4.8, and more preferably 1.5 to 4.

[0024] In Method 1-1, the temperature of the aqueous medium may be 0 to 40 °C, or may be 0 to 25 °C. From the viewpoint of extending the lifetime of the generated active species, it is preferably 0 to 10 °C, and more preferably 0 to 5 °C.

[0025] In Method 1-1, the air is preferably injected into the aqueous medium through a cylinder. In this case, the inner diameter of the cylinder may be 0.1 to 1 mm or 0.3 to 0.7 mm, and the flow rate of the air is preferably 50 to 200 sccm (mL / min), more preferably 70 to 150 sccm (mL / min), from the viewpoint of facilitating stable plasma generation.

[0026] In Method 1-1, the discharge is preferably DC discharge. In this case, the current in DC discharge is preferably 1 to 30 mA, more preferably 5 to 15 mA, from the viewpoint of efficiently generating active species such as active nitrogen species and active oxygen species.

[0027] In Method 1-1, the discharge may be carried out under atmospheric pressure or under low pressure, and is preferably carried out under atmospheric pressure from the viewpoint of ease of operation.

[0028] In Method 1-1, the discharge is preferably a glow discharge. When the discharge is a DC discharge, connecting a limiting resistor to the DC power supply makes it easier to generate a glow discharge. The resistance value of the limiting resistor may be, for example, 30 to 70 kΩ. Furthermore, cooling the electrode used for the discharge during the discharge makes it easier to generate a glow discharge. For example, when air is injected into an aqueous medium through a cylinder, using the cylinder as an electrode also cools the electrode with the air, making it easier to generate a glow discharge. Furthermore, reducing the volume of the generated plasma makes it easier to generate a glow discharge. For example, when air is injected into an aqueous medium through a cylinder, setting the inner diameter of the cylinder and the flow rate of the injected air within the above-mentioned ranges makes it easier to generate a glow discharge.

[0029] In method 1-1, the discharge time may be 1 minute to 3 hours, preferably 5 to 80 minutes, and more preferably 5 to 15 minutes, from the viewpoint of efficiently generating active species such as active nitrogen species and active oxygen species.

[0030] FIG. 1 is a schematic diagram showing an example of an apparatus used in Method 1-1. In FIG. 1, the lower part of the cylindrical electrode 2 is covered by an insulator tube 4. The cylindrical electrode 2 and the insulator tube 4 are cylindrical. The insulator tube 4 extends along the extending direction of the cylindrical electrode 2 from the lower end of the cylindrical electrode 2, and a space is provided below the cylindrical electrode 2. The cylindrical electrode 2 is connected to a DC power source via a conducting wire 32. The platinum electrode 6 is also connected to the above DC power source via the conducting wire 32. The cylindrical electrode 2 and the platinum electrode 6 are installed vertically downward, and at least the lower ends of the insulator tube 4 and the platinum electrode 6 are located in the aqueous medium 22. By discharging air from above the cylindrical electrode 2 downward, air is injected into the aqueous medium 22, and bubbles 24 are formed. By discharging in this bubble 24 by the above DC power source, the air forming the bubble 24 can be used as plasma 12 and the plasma 12 can be brought into contact with the aqueous medium 22. Thereby, plasma-treated water is generated.

[0031] As Method 2, it is preferable to cross two helium flows in the vicinity above the aqueous medium and discharge the helium flow (Method 2-1).

[0032] In Method 2-1, the pH and temperature of the aqueous medium, the discharge is preferably DC discharge, the preferred current of the DC discharge, it is preferably performed under atmospheric pressure, and the discharge is preferably glow discharge, which is the same as the above Method 1.

[0033] In Method 2-1, the intersection angle of the helium flows may be 20 to 100°, or may be 40 to 80°.

[0034] In Method 2-1, the distance between the intersection point of the helium flows and the water surface of the aqueous medium may be 2 to 7 mm.

[0035] In Method 2-1, the helium flow may be ejected from a cylinder with an inner diameter of 0.3 to 0.7 mm. When the helium flow is ejected from the cylinder, from the viewpoint of easily generating plasma stably, the flow rate of the helium gas from the cylinder is preferably 100 to 1200 sccm (mL / min).

[0036] In Method 2-1, when the discharge is a DC discharge, connecting a limiting resistor to the DC power supply makes it easier to form a glow discharge. The resistance value of the above limiting resistor may be, for example, 30 to 70 kΩ. Also, during the discharge, cooling the electrodes used for the discharge makes it easier to form a glow discharge. For example, when injecting a helium flow from a cylinder, by also using the cylinder as an electrode, the electrode is cooled by the helium flow, making it easier to form a glow discharge.

[0037] In Method 2-1, the discharge time may be 20 minutes to 2 hours.

[0038] Figure 2 is a schematic diagram showing an example of the apparatus used in Method 2-1. In Figure 2, two cylindrical electrodes 2 are connected to a power supply via a conducting wire 32. The cylindrical electrode 2 is cylindrical. The two cylindrical electrodes 2 are installed at an inclination from the vertical downward direction such that the plasma 12 irradiated from the lower ends of the cylindrical electrodes 2 intersects. The lower ends of the two cylindrical electrodes 2 are at the same height, and the distance d1 between the lower ends may be 2 to 6 mm. The point where the plasma 12 intersects is above the water surface of the aqueous medium 22. By discharging helium gas from the lower ends of the two cylindrical electrodes 2 and applying a voltage, an electric current flows through the helium gas, and the plasma 12 of the helium gas is generated. The plasma 12 reacts with the air, and the reactant contacts the aqueous medium 22. Thereby, plasma-treated water is generated.

[0039] As Method 2, it is also preferable to inject two helium flows into the aqueous medium and discharge the helium flows (Method 2-2).

[0040] In Method 2-2, the pH and temperature of the aqueous medium, the discharge is preferably a DC discharge, the preferred current of the DC discharge, the discharge is preferably carried out under atmospheric pressure, and the discharge is preferably a glow discharge are the same as those of Method 1 described above.

[0041] In Method 2-2, the inner diameter of the cylinder through which the helium flow is injected, the flow rate of the helium gas, and the discharge time are the same as those in the above-described Method 2-1.

[0042] In Method 2-2, when the discharge is DC discharge, connecting a limiting resistor to the DC power supply makes it easier to form a glow discharge. The resistance value of the above limiting resistor may be, for example, 30 to 70 kΩ. Also, during discharge, cooling the electrodes used for discharge makes it easier to form a glow discharge. For example, when injecting a helium flow from a cylinder, by also using the cylinder as an electrode, the electrode is cooled by the helium flow, making it easier to form a glow discharge.

[0043] FIG. 3 is a schematic diagram showing an example of the apparatus used in Method 2-2. In FIG. 3, two cylindrical electrodes 2 are connected to a power supply via a conducting wire 32. The cylindrical electrode 2 has a cylindrical shape. The two cylindrical electrodes 2 are installed vertically downward such that the plasma 12 irradiated from the lower end of the cylindrical electrode 2 contacts the aqueous medium 22. From the lower ends of the two cylindrical electrodes 2, helium gas is discharged toward the water surface of the aqueous medium 22, and by applying a voltage, a current flows through the two helium gases and the water surface connecting them, generating the plasma 12 of the helium gas. The plasma 12 reacts with air, and the reactant contacts the aqueous medium 22. Thereby, plasma-treated water is generated.

[0044] 〔Hydroxyl Group Introduction Step〕 In the hydroxyl group introduction step, an aromatic compound is brought into contact with the plasma-treated water to introduce a phenolic hydroxyl group into the aromatic compound, generating an aromatic compound having one phenolic hydroxyl group.

[0045] The contact between the aromatic compound and the plasma-treated water may be carried out during the plasma-treated water generation step or after the plasma-treated water generation step. When performing the above contact during the plasma-treated water generation step, it is preferable to use an aqueous medium containing the aromatic compound in the plasma-treated water generation step.

[0046] When the contact between the aromatic compound and the plasma-treated water is carried out after the plasma-treated water generation step, from the viewpoint of extending the lifetime of the active species contained in the plasma-treated water, the time from the end of the plasma treatment to the contact is preferably 5 minutes or less, more preferably 1 minute or less. The temperature of the plasma-treated water during that period may be 0 to 40°C, or may be 0 to 25°C. From the viewpoint of extending the lifetime of the active species contained in the plasma-treated water, it is preferably 0 to 10°C, more preferably 0 to 5°C.

[0047] When the plasma-treated water generation step is carried out by the above-mentioned method 1, it is preferable that the contact between the aromatic compound and the plasma-treated water is carried out after the plasma-treated water generation step. That is, in this case, it is preferable to carry out the plasma-treated water generation step before the hydroxyl group introduction step.

[0048] In this specification, "phenolic hydroxyl group" means a hydroxyl group directly bonded to an aromatic carbon ring. In this specification, "aromatic compound" means an aromatic compound having an aromatic carbon ring and not having a phenolic hydroxyl group.

[0049] Examples of the aromatic compound include benzene, toluene, xylene, ethylbenzene, styrene, divinylbenzene, aniline, benzoic acid, phthalic acid, biphenyl, naphthalene, anthracene, etc., and benzene is preferable.

[0050] Examples of the aromatic compound having one phenolic hydroxyl group include phenol when the aromatic compound is benzene, salicylic acid when it is benzoic acid, cresol when it is toluene, and naphthol when it is naphthalene.

[0051] In the hydroxyl group introduction step, the pH of the plasma-treated water is preferably 1 to 4.8, more preferably 1.5 to 4, from the viewpoint of increasing the content of active species such as peroxynitrous acid. The pH of the plasma-treated water may be adjusted by a pH adjuster such as nitric acid as necessary.

[0052] In the hydroxyl group introduction step, the temperature of the plasma-treated water may be 0 to 40°C, may be 0 to 25°C, and from the viewpoint of extending the lifetime of the active species contained in the plasma-treated water, it is preferably 0 to 10°C, and more preferably 0 to 5°C.

[0053] In the hydroxyl group introduction step, the amount of the aromatic compound with respect to the plasma-treated water may be 1 to 1000 mmol, may be 10 to 100 mmol, may be 10 to 50 mmol, and is preferably 10 to 23 mmol per 1 L of the plasma-treated water.

[0054] In the hydroxyl group introduction step, the time for bringing the aromatic compound into contact with the plasma-treated water may be, for example, 1 minute to 72 hours, may be 3 to 24 hours, or may be 3 minutes to 30 minutes.

Examples

[0055] Examples are given below to explain the present invention in more detail, but the present invention is not limited to these examples.

[0056] Phenol was produced by the method described in the production examples described below. However, the concentrations of phenol, hydrogen peroxide, nitrite ion, nitrate ion, and ammonia were measured by the digital pack test shown below. Also, in the production examples described below, plasma irradiation was performed by the method shown below. For the application of voltage in plasma irradiation, an electric circuit including a variable DC power supply and a 50 kΩ limiting resistor connected in series to the variable DC power supply was used.

[0057] <Digital pack test> The digital pack tests used were the Kyoritsu Rikagaku Kenkyusho Digital Pack Test Phenol (Model DPM2-PNL), Digital Pack Test Hydrogen Peroxide (Model DPM2-H2O2), Digital Pack Test Nitrite / Nitrite Nitrogen (Model DPM2-NO2), Digital Pack Test Nitrate / Nitrate Nitrogen (Model DPM2-NO3), and Digital Pack Test Ammonium / Ammonium Nitrogen (Model DPM2-NH4). The Digital Pack Tests were used according to the Kyoritsu Rikagaku Kenkyusho protocol. However, since the Digital Pack Test Nitrate / Nitrate Nitrogen (Model DPM2-NO3) measures the total concentration of nitrate and nitrite ions in the sample, the nitrate ion concentration was calculated by subtracting the nitrite ion concentration obtained by the Digital Pack Test Nitrite / Nitrite Nitrogen (Model DPM2-NO2) from the measured value. Unless otherwise specified, when measuring a sample with a concentration higher than the upper measurement limit of the Digital Pack Test, the sample was diluted before being subjected to the Digital Pack Test, and the obtained measurement value was multiplied by the dilution factor to determine the concentration in the sample.

[0058] <Plasma irradiation> Plasma irradiation was carried out using the device shown in any one of Figures 1 to 3. Each of these will be explained in detail below.

[0059] The apparatus shown in Fig. 1 and the method of irradiating plasma will be described below. The lower part of the cylindrical electrode 2 was covered with an insulator tube 4. As the cylindrical electrode 2, a metal cylinder with an inner diameter of about 0.5 mm was used. As the insulator tube 4, a cylindrical insulator was used. The insulator tube 4 extended along the extending direction of the cylindrical electrode 2 from the lower end of the cylindrical electrode 2, and a space was provided below the cylindrical electrode 2. The cylindrical electrode 2 was connected to the above-described electric circuit via a conducting wire 32. The platinum electrode 6 was also connected to the above-described electric circuit via the conducting wire 32. The cylindrical electrode 2 and the platinum electrode 6 were installed vertically downward, and the lower ends of the insulator tube 4 and the platinum electrode 6 were positioned in the aqueous medium 22. Air was injected into the aqueous medium 22 by discharging air from above the cylindrical electrode 2 downward to form bubbles 24. By applying a voltage to the bubbles 24 by the above-described electric circuit to cause discharge, the air forming the bubbles 24 was used as plasma 12 and the plasma 12 was brought into contact with the above-described aqueous medium 22. Thereby, plasma-treated water was generated.

[0060] The apparatus shown in Fig. 2 and the method of irradiating plasma will be described below. Two cylindrical electrodes 2 were connected to the above-described electric circuit via a conducting wire 32. As the cylindrical electrode 2, a metal cylinder with an inner diameter of about 0.5 mm was used. The two cylindrical electrodes 2 were installed with an inclination of 30° each from the vertical downward direction so that the plasma 12 irradiated from the lower ends of the cylindrical electrodes 2 intersects at 60°. The two cylindrical electrodes 2 had the same height at the lower ends, and the distance d1 between the lower ends was 4 mm. The point where the plasma 12 intersects is above the water surface of the aqueous medium 22, and the distance d2 between the intersecting point and the water surface was 5 mm. Helium gas was discharged from the lower ends of the two cylindrical electrodes 2, and a voltage was applied to generate plasma 12 of helium gas. By generating the plasma 12, the reactants of the plasma 12 and air came into contact with the aqueous medium 22, and plasma-treated water was generated.

[0061] The apparatus shown in Fig. 3 and the method of irradiating plasma will be described below. Two cylindrical electrodes 2 were connected to the above-described electric circuit via a conducting wire 32. As the cylindrical electrodes 2, metal cylinders with an inner diameter of about 0.5 mm were used. The two cylindrical electrodes 2 were installed vertically downward so that the distance d3 between the lower end of the cylindrical electrode 2 and the water surface of the aqueous medium 22 was 5 mm, such that the plasma 12 irradiated from the lower end of the cylindrical electrode 2 contacted the water surface of the aqueous medium 22. Helium gas was released from the lower ends of the two cylindrical electrodes 2 toward the water surface of the aqueous medium 22, a voltage was applied, and a current was passed through the two helium gases and the water surface connecting them, generating a plasma 12 of helium gas. By generating the plasma 12, the reactants of the plasma 12 and air contacted the aqueous medium 22, and plasma-treated water was generated.

[0062] <Production Example 1: Irradiation of Plasma onto an Aqueous Solution Containing Benzene> (Production Example 1A-1) 3 mL of benzene was added to 200 mL of purified water to obtain a benzene aqueous solution of 23 mmol / L. This benzene aqueous solution was placed in a beaker and stirred with a stirrer, and the benzene aqueous solution was irradiated with plasma as the aqueous medium 22 by the method shown in Fig. 2 above. During the plasma irradiation, the benzene aqueous solution as the aqueous medium 22 was maintained at a temperature of 20 - 25°C and a pH of 6 - 8. The flow rate of helium released from the two cylindrical electrodes 2 in Fig. 2 was 800 mL / min, and the applied voltage was a current of 13 mA and a voltage of 1.15 kV.

[0063] The plasma irradiation of the above benzene aqueous solution was performed for 60 minutes. From the start of the plasma irradiation to 60 minutes later, 1.5 mL of the benzene aqueous solution was taken out every 6 minutes, and the concentration of phenol was measured by a digital pack test. The results are shown in Fig. 4.

[0064] (Production Example 1A-2) To 9.85 mL of each of two purified waters, 0.15 mL of benzene was added to obtain two 23 mmol / L benzene aqueous solutions. These benzene aqueous solutions were placed in separate beakers and irradiated with plasma using the method shown in FIG. 2 above while mixing with a stirrer, with each benzene aqueous solution serving as the aqueous medium 22. During the plasma irradiation, the benzene aqueous solution as the aqueous medium 22 was maintained at a temperature of 20 - 25°C and a pH of 6 - 8. The flow rate of helium released from the two cylindrical electrodes 2 in FIG. 2 was 800 mL / min, and the applied voltage was 1.15 kV with a current of 13 mA.

[0065] After irradiating the above two benzene aqueous solutions with plasma for 8 minutes and 16 minutes respectively, the concentration of phenol was measured by a digital pack test. The results are shown in FIG. 5.

[0066] (Production Example 1B) To 98.5 ml of purified water, 1.5 mL of benzene was added to obtain a 23 mmol / L benzene aqueous solution. This benzene aqueous solution was placed in a beaker and irradiated with plasma using the method shown in FIG. 3 above while mixing with a stirrer, with the benzene aqueous solution serving as the aqueous medium 22. During the plasma irradiation, the benzene aqueous solution as the aqueous medium 22 was maintained at a temperature of 20 - 25°C and a pH of 6 - 8. The flow rate of helium released from the two cylindrical electrodes 2 in FIG. 3 was 800 mL / min, and the applied voltage was 1.15 kV with a current of 13 mA.

[0067] The plasma irradiation of the above benzene aqueous solution was carried out for 30 minutes. At 11 minutes, 23 minutes, and 30 minutes after the start of plasma irradiation, 1.5 mL of the benzene aqueous solution was taken out, and the concentration of phenol was measured by a digital pack test. The results are shown in FIG. 6.

[0068] As shown in FIGS. 4 - 6, the generation of phenol was confirmed in all of Production Examples 1A - 1, 1A - 2, and 1B.

[0069] <Production Example 2: Mixing of Plasma - Treated Water and Benzene> (Production Example 2A) 30 mL of purified water was prepared, and the purified water was irradiated with plasma as the aqueous medium 22 by the method shown in FIG. 2 above. During the irradiation of the plasma, the purified water as the aqueous medium 22 was maintained at a temperature of 20 to 25 °C and a pH of 6 to 8. The flow rate of helium released from the two cylindrical electrodes 2 in FIG. 2 was 600 mL / min, and the applied voltage was a current of 10 mA and a voltage of 2 kV.

[0070] By irradiating the purified water with plasma for 30 minutes as described above, plasma-treated water was obtained. Of the above plasma-treated water immediately after the 30-minute irradiation, 10 mL was mixed with 0.5 mL of benzene so that the final concentration of benzene was 23 mmol / L, and the mixture was subjected to a digital pack test 10 minutes after the mixing, and the measurement after the benzene mixing was performed. During the mixing of the above plasma-treated water and benzene, the plasma-treated water was maintained at a temperature of 20 to 25 °C and a pH of 6 to 8. The remaining approximately 20 mL was subjected to a digital pack test immediately after the irradiation without mixing with benzene, and the measurement immediately after the irradiation was performed. Table 1 shows the concentrations of phenol, hydrogen peroxide, nitrite ion, nitrate ion, and ammonia immediately after the irradiation and after the benzene mixing, measured by the digital pack test.

[0071]

Table 1

[0072] (Production Example 2B) 30 mL of purified water was prepared, and the purified water was irradiated with plasma as the aqueous medium 22 by the method shown in FIG. 3 above. During the irradiation of the plasma, the purified water as the aqueous medium 22 was maintained at a temperature of 20 to 25 °C and a pH of 6 to 8. The flow rate of helium released from the two cylindrical electrodes 2 in FIG. 3 was 200 mL / min, and the applied voltage was a current of 7 mA and a voltage of 2.6 kV.

[0073] As described above, plasma was irradiated to purified water for 30 minutes to obtain plasma-treated water. Of the plasma-treated water immediately after the 30-minute irradiation, 1.5 mL was subjected to a digital pack test without mixing with benzene to measure the concentration of nitrite ions, and the remainder was mixed with 0.5 mL of benzene so that the final concentration of benzene became 23 mmol / L, and the mixture was subjected to a digital pack test 10 minutes after the mixing to measure the concentration of phenol. During the mixing of the above plasma-treated water and benzene, the plasma-treated water was maintained at a temperature of 20 to 25°C and a pH of 6 to 8. The concentration of the above nitrite ions was 0.8 mmol / L or more, and the concentration of the above phenol was 0.55 mmol / L.

[0074] (Production Example 2C) Salt was added to purified water to obtain 30 mL of 17 mmol / L saline. This saline was placed in a beaker and plasma was irradiated to the saline as the aqueous medium 22 by the method shown in FIG. 1 above. During the irradiation of the plasma, the saline as the aqueous medium 22 was maintained at a temperature of 0 to 10°C and a pH of 6 to 8, the flow rate of the air released from the cylindrical electrode 2 in FIG. 1 was 71 mL / min, and the application of the voltage was carried out at a current of 13 mA and a voltage of 1.3 kV.

[0075] As described above, plasma was irradiated to purified water for 80 minutes, and from the start of the irradiation to 80 minutes later, 1.5 mL was subjected to a digital pack test over time to measure the concentrations of nitrite ions and hydrogen peroxide at each time. The results are shown in FIGS. 7(a) and (b), respectively.

[0076] As shown in Fig. 7(a), when the plasma was irradiated for about 7 minutes by the above method, it was shown that plasma-treated water containing nitrite ions at a high concentration could be obtained. Therefore, by the above method, 30 mL of 17 mmol / L saline was irradiated with plasma for 7 minutes to obtain plasma-treated water, and immediately thereafter, 0.062 mL of benzene was mixed with the plasma-treated water so that the final concentration of benzene became 23 mmol / L. During the mixing of the above plasma-treated water and benzene, the plasma-treated water was maintained at a temperature of 0 to 10 °C and a pH of 2 to 4. From the start of mixing to 1400 minutes later, 1.5 mL was subjected to a digital pack test over time to measure the concentration of phenol at each time. The results are shown in Fig. 8.

[0077] In any of Production Examples 2A to 2C, the formation of phenol was confirmed. As shown in Fig. 8, in Production Example 2C, a phenol solution with a concentration of 0.1 mmol / L or higher could be obtained. Also, in Production Examples 2A and 2C, as shown in Table 1 and Figs. 7(a) and (b), since each plasma-treated water contains nitrite ions and hydrogen peroxide, there is a possibility that peroxynitrous acid is generated.

Explanation of Signs

[0078] 2... Cylindrical electrode, 4... Insulating tube, 6... Platinum electrode, 12... Plasma, 22... Aqueous medium, 24... Bubbles, 32... Conductive wire.

Claims

1. A method for producing an aromatic compound having one phenolic hydroxyl group, comprising a hydroxyl group introduction step of introducing a phenolic hydroxyl group into the aromatic compound by bringing the aromatic compound into contact with plasma-treated water.

2. The aromatic compound is benzene, The production method according to claim 1, wherein the aromatic compound having one phenolic hydroxyl group is phenol.

3. The production method according to claim 1 or 2, further comprising a plasma-treated water generation step of forming bubbles by injecting air into an aqueous medium and generating the plasma-treated water by discharging in the bubbles before the hydroxyl group introduction step.

4. The production method according to claim 1 or 2, wherein the pH of the plasma-treated water is 1 to 4.8.

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