Chemical reaction method and reaction device

Abstract

To provide a method and a device for efficiently chemically reacting a polar solute and a non-polar solute.SOLUTION: A method emits light from a light source, to a mixed liquid in which a first solution mainly containing a polar solute and a second solution mainly containing a non-polar solute are mixed, and additionally supplies a precursor of the polar solute, on the basis of means for estimating by light reflecting at least one of the concentration of the non-polar solute and the concentration of the polar solute with the first solution or light transmitting the first solution, or other sensors. The device has: a light irradiation part for emitting light from a light source to the mixed liquid; a precursor supply part for additionally supplying the precursor of the polar solute; a detection part for detecting reflection light or transmission light from the first solution; and a calculation part for determining the supply amount of the precursor supplied by the precursor supply part, on the basis of at least the one of the estimated concentration of the non-polar elute and concentration of the polar elute.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a chemical reaction method and a reaction apparatus. [Background technology]

[0002] The use of light to chemically react polar and non-polar solutes is known in a variety of fields.

[0003] For example, Patent Document 1 describes a technology for decomposing dioxins by mixing and stirring a non-polar solute in which dioxins have been dissolved with alcohol (a polar solute), and irradiating the mixture with ultraviolet light (UV 250 nm) from a low-pressure mercury lamp. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-068227 Summary of the Invention [Problem to be solved by the invention]

[0005] The efficiency of a chemical reaction is affected by various factors, such as the irradiation conditions of light such as ultraviolet light, the amount of reactants, the environment of the reaction site, etc. The object of the present invention is to provide a method for efficiently carrying out a chemical reaction in a mixture of a non-polar solute and a polar solute, and a reaction device for efficiently carrying out a chemical reaction in a mixture containing a non-polar solute and a polar solute. [Means for solving the problem]

[0006] The present invention provides a method for chemically reacting a polar solute with a non-polar solute, the method comprising: A mixed solution obtained by mixing a first solution mainly containing the polar solute and a second solution mainly containing the non-polar solute is irradiated with light from a light source, and a precursor of the polar solute is additionally supplied based on a means for estimating the amount of the non-polar solute and / or the amount of the polar solute by light reflected from the first solution, light transmitted through the first solution, or by another sensor.

[0007] As will be described in detail later, in this method, light from a light source imparts energy to a polar solute, converting it into an activated species. Hereinafter, activated species may be referred to as radicals. When the polar solute is ClO2 (chlorine dioxide), light energy from the light source generates a chlorine radical, which is an activated species of chlorine atoms. The generated chlorine radical then abstracts one hydrogen atom from CH4 (methane). The methane from which one hydrogen atom has been abstracted becomes CH3 (methyl radical). The methyl radical combines with an oxygen molecule to form CH3O2 (methylperoxy radical). As will be described in detail later, the methylperoxy radical is an intermediate in a series of chemical reactions that leads from the reactant methane to the final product, methanol or formic acid, and its production should be promoted to improve the efficiency of the series of chemical reactions.

[0008] This chemical reaction converts chlorine dioxide, a polar solute in the mixed solution, into HCl (hydrogen chloride). In other words, as the chemical reaction progresses, the amount of chlorine dioxide in the mixed solution decreases. This decrease in chlorine dioxide results in a shortage of chlorine radicals for decomposing methane. Therefore, in the above method, NaClO2 (sodium chlorite), a chlorine dioxide precursor (hereinafter, the precursor of the polar solute may be simply referred to as the "precursor"), is additionally supplied. Sodium chlorite combines with hydrogen chloride in the mixed solution to generate chlorine dioxide, and light from a light source increases the number of chlorine radicals. As the number of chlorine radicals increases, the amount of methylperoxy radicals produced from methane increases, improving the efficiency of the chemical reaction.

[0009] As mentioned above, sodium chlorite is a source of chlorine radicals. To increase the number of methylperoxy radicals, a large amount of chlorine radicals is required. To generate a large amount of chlorine radicals, a polar solute, chlorine dioxide, and thus sodium chlorite, a precursor of chlorine dioxide, are required in large amounts.

[0010] However, the present inventors have discovered that it is preferable to supply the precursor (sodium chlorite) in multiple portions rather than all at once at the beginning. Through extensive research, the present inventors have found that the amount of additional precursor supplied is not necessarily greater, but that there is an optimal supply amount. As will be described in detail later, it has been found that the optimal supply amount can be determined based on at least one of the amount of nonpolar solute and the amount of polar solute present. The means for estimating at least one of the amount of nonpolar solute and the amount of polar solute present includes a sensor that detects light reflected by the first solution or light transmitted through the first solution, or another sensor. This allows the chemical reaction to be more efficient.

[0011] As described above, in the "method for chemically reacting a polar solute and a non-polar solute," a precursor of the polar solute is additionally supplied while irradiating light from a light source. This means that the light irradiation and the additional supply of precursor do not necessarily have to be performed simultaneously. In other words, the timing of the light irradiation and the timing of the additional supply of precursor do not have to overlap in time. For example, the additional supply of precursor may be performed after the light irradiation is stopped. Of course, the timing of the light irradiation and the timing of the additional supply of precursor may overlap in time.

[0012] In addition, a plan for additional supply of the precursor of the polar solute may be set in advance based on the amount of the non-polar solute present, for example, the plan for additional supply includes the number of times, the interval between supplies, and the amount of each supply of the precursor.

[0013] One type of sensor used to estimate at least one of the abundance of the nonpolar solute and the abundance of the polar solute is an optical sensor. For example, light is emitted toward the first solution, and the intensity of the light reflected by or transmitted through the first solution is detected by the optical sensor. The amount of the polar solute is determined from the detected light intensity. If the polar solute in the first solution is colored, the color intensity of the polar solute may be detected by a sensor or the naked eye. The darker the color of the first solution, the greater the amount of polar solute in the first solution. Note that the first solution containing chlorine dioxide is yellow, and the higher the concentration of chlorine dioxide, the darker the yellow, and the lower the concentration of chlorine dioxide, the lighter the yellow. The optical sensor includes a detector that measures light intensity or wavelength, or an image sensor (e.g., a CMOS sensor or a CCD sensor). The sensor used to estimate at least one of the abundances of the polar solute may be "other sensors" other than an optical sensor. Examples of "other sensors" include a concentration sensor that measures the concentration of a substance, a pH sensor that measures the acidity of a substance, a temperature sensor that measures the temperature of a substance, a conductivity sensor that measures the conductivity of a substance, and a pressure sensor that measures the pressure of a container filled with a substance. Substances to be detected include a first solution, a second solution, a polar solute that will later be mixed into the mixed liquid, and a non-polar solute that will later be mixed into the mixed liquid. A variety of detectors that detect various physical properties of these substances can be used as sensors used to estimate at least one of the amount of the non-polar solute and the amount of the polar solute.

[0014] The molar concentration of the polar solute precursor supplied may be 10 times or more higher than the molar concentration of the polar solute produced. The precursor is supplied in a state dissolved in a polar solvent. If the polar solute is in a high concentration in the supplied solution, the polar solute can be increased while suppressing the increase in the amount of polar solvent. As a result, the post-reaction products (formic acid and methanol) can be extracted at high concentrations.

[0015] The precursor may be additionally supplied while stirring using a stirrer provided in the vessel into which the precursor is additionally supplied, which allows the precursor concentration to be quickly homogenized after the precursor is supplied, thereby accelerating the reaction to produce the polar solute.

[0016] The container for additionally supplying the precursor and the container for containing the mixed solution and for irradiating the light may be the same. Since the place where the polar solute is generated from the precursor and the place where the active species is generated from the polar solute by irradiating the light are the same, a series of reactions occurs quickly.

[0017] The first solution and the second solution are mixed in a mixing section; The mixed liquid mixed in the mixing section may be irradiated with the light by a light irradiation section located downstream of the mixing section.

[0018] The mixed liquid after the light irradiation may be recovered, the recovered mixed liquid may be separated into the first solution and the second solution, and the separated first solution and second solution may be mixed again in the mixing section.

[0019] The recovered mixed solution may be separated into two layers in the recovery tank, and the first solution may be extracted from the upper layer, and the second solution may be extracted from the lower layer.

[0020] The recovered mixed liquid may be sent to a first liquid tank and a second liquid tank, a precursor of the polar solute may be additionally supplied to the first liquid tank to form a new first solution, and a non-polar solute may be additionally supplied to the second liquid tank to form a new second solution, and the new first solution and the new second solution may be mixed again in the mixing section.

[0021] The mixing section may mix the first solution and the second solution by ejecting the other solution into a narrow channel that guides the other solution.

[0022] The present invention provides an apparatus for chemically reacting a polar solute with a non-polar solute, the apparatus comprising: a light irradiation unit that irradiates a mixed solution obtained by mixing the first solution mainly containing the polar solute and the second solution mainly containing the non-polar solute with light from a light source; a precursor supply unit that additionally supplies a precursor of the polar solute; a detector that detects reflected light or transmitted light from the first solution using a light receiving unit or other sensor to estimate at least one of the amount of the non-polar solute and the amount of the polar solute; The liquid mixture containing the additionally supplied precursor is generated by a calculation unit that determines the amount of the precursor to be supplied by the precursor supply unit based on at least one of the estimated amount of the non-polar solute and the estimated amount of the polar solute.

[0023] The "light receiving unit for detecting reflected light or transmitted light from the first solution" is an optical sensor. Note that the apparatus may have a memory unit including at least one of a table showing a correspondence relationship between the amount of the non-polar solute and a plan for additional supply of a precursor of the polar solute, and an algorithm for determining a plan for additional supply of a precursor of the polar solute from the amount of the non-polar solute.

[0024] The container for additionally supplying the precursor may also be used as the container irradiated with light from the light irradiating unit.

[0025] The vessel into which the precursor is additionally supplied may be equipped with a stirrer.

[0026] A mixing section may be provided that is located upstream of the light irradiation section and mixes the first solution and the second solution.

[0027] The mixing section may mix the first solution and the second solution by ejecting the other solution into a narrow channel that guides the other solution.

[0028] At least one recovery tank may be provided for recovering the mixed liquid after light irradiation, and the light irradiation unit may irradiate the mixed liquid recovered in the recovery tank with light again. [Effects of the Invention]

[0029] This makes it possible to provide a method for efficiently carrying out a chemical reaction on a mixed solution of a non-polar solute and a polar solute, and a reaction apparatus for efficiently carrying out a chemical reaction on a mixed solution containing a non-polar solute and a polar solute. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 shows a first embodiment of a reactor. [Figure 2] FIG. 1 illustrates the main chemical reactions. [Figure 3] This is a model of the time change in chlorine dioxide concentration. [Figure 4] FIG. 2 is a control block diagram of the reaction apparatus. [Figure 5] FIG. 1 is a cross-sectional view taken along a horizontal plane intersecting the stirring bar. [Figure 6] FIG. 2 shows a second embodiment of the reactor. [Figure 7] FIG. 10 shows a third embodiment of the reactor. [Figure 8] FIG. 10 is an enlarged view of a mixing section in a reaction apparatus according to a third embodiment. [Figure 9] FIG. 10 is an enlarged view of a light irradiation unit in a reaction device according to a third embodiment. [Figure 10] FIG. 10 shows a fourth embodiment of the reactor. [Figure 11] FIG. 10 shows a fifth embodiment of the reactor. [Figure 12] FIG. 1 is a diagram showing a reaction apparatus used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0031] <Terminology> First, the terms used in this specification will be explained. Polarity refers to the imbalance of electric charges in the molecules that make up a substance. A polar solute is a substance that has polarity and can be dissolved in a polar solvent. In the embodiment described below, chlorine dioxide (ClO2) is used as the polar solute, but polar solutes other than chlorine dioxide may also be used. Strictly speaking, ClO2 exists as OClO and ClOO, and both OClO and ClOO are polar solutes.

[0032] A polar solvent is a substance that has polarity and can dissolve polar solutes. In the embodiment described below, H2O (water) is used as the polar solvent, but polar solvents other than water may also be used. Examples of polar solvents include hydrochloric acid, alcohol, or an alcohol aqueous solution. The alcohol contained in the alcohol or alcohol aqueous solution preferably has a carbon number of 10 or less. In particular, the alcohol contained in the alcohol or alcohol aqueous solution is preferably methanol, ethanol, or butanol.

[0033] In this specification, the first solution mainly containing a polar solute is an aqueous ClO2 solution. In this specification, the expression "mainly containing" refers to the substance that is most abundant among the substances dissolved in the solvent.

[0034] A precursor of a polar solute refers to a reactant in a chemical reaction that produces the polar solute. When the polar solute is chlorine dioxide, sodium chlorite is a precursor. As will be explained in more detail later, sodium chlorite reacts with hydrogen chloride in the mixture to produce chlorine dioxide, a polar solute.

[0035] A nonpolar solute is a substance that has no polarity or is less polar than a polar solute. A nonpolar solute is a substance that dissolves in a nonpolar solvent. In the embodiment described below, methane is used as a nonpolar solute, but a nonpolar solute other than methane may also be used. The nonpolar solute may also be a hydrocarbon other than methane, a fluorocarbon, or a fluorohydrocarbon. The nonpolar solute is preferably a substance that does not have an unsaturated bond. Examples of nonpolar solutes include hydrocarbons such as ethane or propane, fluorocarbons such as perfluoromethane and perfluoroethane, or fluorohydrocarbons such as fluoromethane and fluoroethane. The nonpolar solute is preferably a substance that is gaseous at room temperature and normal pressure.

[0036] A nonpolar solvent is a substance that has no polarity or is less polar than a polar solute and dissolves the nonpolar solute. In this embodiment, perfluorooctane (hereinafter sometimes referred to as "PFO") is used, but nonpolar solvents other than PFO may also be used. In this embodiment, the second solution mainly containing a nonpolar solute is a PFO solution mainly containing methane. In addition to PFO, examples of nonpolar solvents include hydrocarbons, fluorocarbons, and fluorohydrocarbons. The nonpolar solvent is preferably a substance without unsaturated bonds. Examples of nonpolar solvents include hexane, cyclohexane, n-decane, n-octane, n-nonane, octane, isooctane, perfluorohexane, tetradecafluorohexane, perfluoroheptane, perfluorooctane, octadecafluorooctane, perfluorononane, eicosafluorononane, and perfluorodecalin. The nonpolar solvent is preferably a substance that is liquid at room temperature and normal pressure.

[0037] Polar solutes dissolve easily in polar solvents, while nonpolar solutes dissolve easily in nonpolar solvents. The reason why polar solutes dissolve easily in polar solvents is thought to be because polar molecules dissolve together due to electrostatic forces. The reason why nonpolar solutes dissolve easily in nonpolar solvents is because nonpolar molecules dissolve together due to intermolecular dispersion forces. In particular, when it comes to nonpolar molecules, it is thought that they dissolve more easily in solvents with larger molecules than in solvents with smaller molecules. However, polar solutes can dissolve in nonpolar solvents, albeit in small amounts, due to inductive forces.

[0038] A mixture containing a polar solute and a nonpolar solute is a mixture of a first solution containing a polar solute and a polar solvent and a second solution containing a nonpolar solute and a nonpolar solvent. However, for example, under high pressure, a high concentration of polar solute may dissolve in a nonpolar solvent, albeit to a small extent, and a nonpolar solvent may contain a polar solute. The reverse is also true. In other words, a polar solvent may contain a small amount of nonpolar solute.

[0039] Next, embodiments will be described with reference to the drawings as appropriate. Note that all drawings are schematic, and the dimensional ratios in the drawings do not necessarily correspond to the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily correspond to the actual dimensional ratios.

[0040] First Embodiment [Outline of the reactor] FIG. 1 is a diagram illustrating a first embodiment of a reaction apparatus. The reaction apparatus 100 is an apparatus for chemically reacting a polar solute and a non-polar solute. The reaction apparatus 100 includes a reaction vessel (1, 2) that holds a mixed solution containing a polar solute and a non-polar solute, and a light irradiation unit (3, 4). The reaction vessel (1, 2) includes a reaction vessel body 1 and a lid 2. The lid 2 is opened, and the mixed solution is poured into the body 1 through the opening of the cylindrical body 1 with a bottom, and the lid 2 is closed. The shapes of the body 1 and lid 2 shown in FIG. 1 are merely examples, and the present invention is not limited to these shapes. The light irradiation unit (3, 4) includes a light source 4 and a light guide unit 3 that guides light from the light source 4 into the interior of the reaction vessel. Note that the reaction apparatus 100 itself does not necessarily have to include the light source 4. The light source 4 will be described in detail below. The reaction vessel body 1 includes a reflective film 7 on its inner surface that reflects light L1. The reflective film 7 will be described in detail below.

[0041] In this embodiment, the mixed solution includes a first solution S1 and a second solution S2. The first solution S1 is a ClO2 aqueous solution (chlorine dioxide aqueous solution) containing a polar solute in a polar solvent. The second solution S2 is a methane-containing PFO solution containing methane, a nonpolar solute, in PFO, a nonpolar solvent.

[0042] In the reaction vessel, the first solution S1 and the second solution S2 are insoluble in each other and undergo phase separation. The specific gravities of the first solution S1 and the second solution S2 are different. Therefore, the first solution S1 and the second solution S2 exist separately in the reaction vessel, and an interface BS is formed between the first solution S1 and the second solution S2. In this embodiment, the specific gravity of the first solution S1 is lower than the specific gravity of the second solution S2, so the layer of the first solution S1 is located above the layer of the second solution S2.

[0043] An interface also exists in addition to the interface BS formed between the layered first solution S1 and layered second solution S2. When the first solution S1 and the second solution S2 are stirred by a stirrer 5 (described later), granular first solution S1 appears in the layer of the second solution S2. An interface also exists between the granular second solution S2 and the first solution S1 around it.

[0044] Light L1 is emitted from each of two light sources 4 through the light guide 3 toward the interface BS between the first solution S1 and the second solution S2 in the reaction vessel. Light L1 initiates a photochemical reaction at the interface between the two layers. The advantage of photochemical reactions in two liquid layers is that they enable a chemical reaction between polar and non-polar substances. Additionally, if oxygen is required for a chemical reaction, the amount of oxygen present in the air poses a risk of ignition or explosion upon application of light energy. However, the amount of oxygen present in the liquid can be limited, reducing the risk of ignition or explosion upon application of light energy. Details of photochemical reactions are discussed below. Stirring the mixed solution (S1 + S2) with the stirrer 5 increases the total interfacial area, accelerating the photochemical reaction.

[0045] The reaction apparatus 100 of this embodiment further includes a stirrer 5, a power source 6 for the stirrer 5, a gas phase component jet 8, a gas phase component supply pump 9, a methane supply valve (non-polar solute supply valve) 10 connected to a methane supply source (non-polar solute supply source) 50, a precursor supply unit 11, a precursor supply pump 12 that delivers a solution containing the precursor, a concentration detector 13 for the first solution, and a control unit 15, the details of which will be described later. The vessels (1, 2) included in the reaction apparatus 100 are vessels that serve both as a vessel for additionally supplying the precursor and as a vessel that is irradiated with light from a light irradiation unit.

[0046] [Chemical reaction mechanism] FIG. 2 is a diagram showing the main chemical reactions that occur in the chemical reaction method and chemical reaction apparatus of this embodiment. The chemical reaction mechanism of this embodiment will be described with reference to FIG. 2. First, an aqueous solution of sodium chlorite (NaClO2) and hydrochloric acid, which is an aqueous solution of hydrogen chloride (HCl), are supplied into the main body 1 of the reaction vessel. As shown by chemical reaction R1 in FIG. 2, chlorine dioxide (ClO2) is produced from sodium chlorite (NaClO2) and hydrogen chloride (HCl). This chemical reaction is shown in equation (1). Both sodium chlorite and chlorine dioxide are polar solutes, and hydrochloric acid is a polar solvent. 5NaClO2 + 4HCl → 4ClO2 + 4Na ++4Cl ― +2H2O (1)

[0047] The following chemical reaction R2 will be explained. The generated chlorine dioxide (ClO2) easily absorbs the light L1 emitted by the light source 4. When the energy of the light L1 is given to chlorine dioxide, it generates chlorine radicals (Cl), which are activated species of chlorine atoms. This chemical reaction is shown in equation (2). ClO2 → Cl+O2 (2)

[0048] The photochemical reaction in equation (2) is the initial reaction, which triggers a chain reaction of subsequent reactions. Chemical reaction R3 is a process in which a chlorine radical abstracts a hydrogen atom from methane, producing a methyl radical (hereafter simply referred to as "methyl"), which is an active species of the methane molecule. This chemical reaction is shown in equation (3). Cl + CH4 → CH3 + HCl (3)

[0049] Chemical reaction R3 occurs at the interface BS between the two solutions (S1, S2) mentioned above or at the interface of each particle. In particular, chlorine radicals generated by the initial reaction near the interface of the first solution S1 react with methane (CH4) in the second solution S2 near the interface, producing methyl (CH3) and hydrogen chloride (HCl). Chemical reaction R3 is also called an interfacial reaction.

[0050] The methyl radical produced combines with an oxygen molecule (O2) in the second solution S2 in chemical reaction R4, producing the intermediate methylperoxy radical (CH3O2). Chemical reaction R4 is shown in equation (4). M represents a third element. CH3+O2+M → CH3O2+M (4)

[0051] Methylperoxyl radicals are intermediates that play an important role in the fixation of methane. When methylperoxyl radicals (CH3O2) come into contact with each other in solution, they produce methanol (CH3OH) and formaldehyde (HCHO) according to equation (5). Formaldehyde undergoes an oxidation reaction in which it gradually combines with oxygen atoms contained in oxygen molecules in the reaction vessel to produce formic acid (HCOOH). The reaction that produces methanol and formaldehyde from methylperoxyl radicals is chemical reaction R5. 2CH3O2→ CH3OH+HCHO+O2···(5)

[0052] In some cases, methylperoxy radicals (CH3O2) come into contact with each other in a solution, and through chemical reaction R6, an oxygen molecule is released to produce methoxy (CH3O). Chemical reaction R6 is shown in equation (6). 2CH3O2 → 2CH3O+O2 (6)

[0053] When the methoxy groups obtained in equation (6) come into contact with each other, methanol (CH3OH) and formaldehyde (HCHO) are produced according to equation (7). As mentioned above, formaldehyde is oxidized to form formic acid (HCOOH). The reaction that produces methanol and formaldehyde from methoxy groups is chemical reaction R7. 2CH3O → CH3OH+HCHO ···(7)

[0054] [The usefulness of methane fixation] The series of chemical reactions described above has two benefits. The first benefit is the immobilization of methane. Methane gas is produced in large quantities from, for example, food waste and livestock excrement. Methane gas is known as a greenhouse gas that causes global warming. If released directly into the atmosphere, its global warming potential is said to be 25 times that of carbon dioxide. It is also well known that methane gas can be burned to power engines and used in boilers, but this use of methane releases large amounts of carbon dioxide into the atmosphere. Methane gas is a gas at room temperature and pressure, but transporting it as a gas is inefficient and difficult to store. Immobilizing methane gas reduces greenhouse gas emissions and improves its transport efficiency and storage, contributing to global warming countermeasures.

[0055] The second benefit is that the substances produced by the immobilization are industrially useful substances, namely, methanol and formic acid. Profits from providing these substances to the market can be expected, attracting investment in the introduction of the chemical reaction apparatus and chemical reaction method described above. In other words, methane immobilization can be a viable business.

[0056] Providing the reactor of this embodiment and carrying out the chemical reaction of this embodiment to produce methanol and formic acid from methane gas will contribute to achieving Goal 13 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "take urgent action to combat climate change and its impacts."

[0057] [Additional supply of polar solute precursors] The photochemical reaction (chemical reaction R3) that produces methyl from methane mentioned above is also a reaction that consumes chlorine radicals (Cl) produced by light L1. To continuously produce methyl, it is necessary to produce and store a large amount of chlorine radicals so that the number does not decrease.

[0058] However, chlorine radicals cannot be produced and stored in large quantities because, as the amount of chlorine radicals in the solution increases, the chances of chlorine radicals coming into contact with other chlorine radicals increase before they come into contact with methane molecules, resulting in the formation of chlorine molecules (Cl2).Chlorine molecules cannot activate methane to methyl.

[0059] Since it is not possible to produce and store a large amount of chlorine radicals, it is necessary to continuously supply chlorine radicals to prevent the chlorine radical concentration from decreasing. To do this, it is necessary to prepare a large amount of chlorine dioxide, which is the raw material for chlorine radicals.

[0060] Figure 3 shows a time-dependent change model of the chlorine dioxide concentration in the chlorine dioxide aqueous solution, which is the first solution S1. To prepare a large amount of chlorine dioxide, which is the raw material for chlorine radicals, first set the concentration C2 (for example, 300 mM (mmol / L = mmol / dm 3 Two methods are possible: Method M1 (shown by the dashed line in Figure 3), in which a highly concentrated aqueous solution of chlorine dioxide is prepared, and Method M2 (shown by the thick line in Figure 3), in which chlorine dioxide is replenished when the chlorine dioxide concentration drops.

[0061] Method M1 is a simple method because it does not require replenishment of chlorine dioxide. However, initially, starting from a concentration of C2, light L1 generates more chlorine radicals than necessary relative to the amount of methane, resulting in the production of unnecessary chlorine molecules. In addition, there is an upper limit to the solubility of chlorine dioxide in water, a nonpolar solvent. If the solubility of chlorine dioxide increases beyond this upper limit, chlorine dioxide will be generated in the gas phase, increasing the risk of explosion. Furthermore, if the chlorine dioxide concentration decreases and falls below concentration C0 (e.g., concentration C0 is 80 mM), the production efficiency of the products, formic acid and methanol, will decrease significantly.

[0062] Therefore, we employ method M2, which replenishes chlorine dioxide when the chlorine dioxide concentration drops. In method M2 of FIG. 3, for example, the chlorine dioxide starts at concentration C1. As chlorine dioxide is consumed with irradiation of light L1, chlorine dioxide is replenished to restore the concentration when it approaches concentration C0. This ensures constant and stable generation of chlorine radicals. Concentration C1 is preferably, for example, between 80 mM and 200 mM, and more preferably between 80 mM and 150 mM. Furthermore, for safer use of chlorine dioxide, a concentration of between 80 mM and 120 mM is most preferred.

[0063] In this embodiment, chlorine dioxide is not replenished by supplying chlorine dioxide itself, but by additionally supplying sodium chlorite (NaClO2), a precursor of chlorine dioxide. Supplying chlorine dioxide itself increases the risk of explosive combustion, especially when the chlorine dioxide aqueous solution being supplied is highly concentrated. In contrast, supplying sodium chlorite hardly increases the risk of explosive combustion. While hydrogen chloride is consumed to generate chlorine dioxide (see chemical reaction R1 and formula (1) in FIG. 2), hydrogen chloride is generated in chemical reaction R3 (see chemical reaction R3 and formula (3) in FIG. 2), so the hydrogen chloride concentration does not decrease significantly. Therefore, even without supplying hydrogen chloride, chemical reaction R1 proceeds simply by additionally supplying sodium chlorite, and chlorine dioxide is replenished.

[0064] [Precursor supply section] Returning to FIG. 1, the precursor supply unit 11 provided in the reaction apparatus 100 will be described. The precursor supply unit 11 has a reservoir tank for a sodium chlorite aqueous solution. The precursor supply unit 11 is connected to a reaction vessel via a precursor supply pump 12. The precursor supply pump 12 is driven to supply a desired amount of a sodium chlorite aqueous solution, which is the precursor, to the reaction vessel at a desired timing. Since the reaction vessel is a vessel that is irradiated with light L1, in the case of the reaction apparatus 100 shown in FIG. 1, the vessel that additionally supplies the precursor and the vessel that contains the mixed solution and is irradiated with the light are the same.

[0065] The sodium chlorite in the sodium chlorite aqueous solution to be supplied is of high concentration. The molar concentration of sodium chlorite in the sodium chlorite aqueous solution may be 10 times or more higher than the molar concentration of chlorine dioxide in the chlorine dioxide aqueous solution to be produced. A high concentration of sodium chlorite means that the amount of water supplied can be reduced, so the mixed solution in the reaction vessel is also of high concentration, and the product formic acid and methanol can be extracted at high concentrations. In the case of a sodium chlorite aqueous solution, the concentration is 1.0 M (mol / L = mol / dm 3 ) or more molar concentration.

[0066] The additional supply of sodium chlorite aqueous solution is preferably based on at least one of the amount of methane supplied to the reactor and the amount of chlorine dioxide present. If the amount of chlorine dioxide present is low, additional sodium chlorite aqueous solution must be supplied to replenish the chlorine dioxide. The reason why the amount of chlorine radicals required is based on the amount of methane supplied to the reactor is that the amount of chlorine radicals required is determined according to the amount of methane that needs to be decomposed. As mentioned above, generating more chlorine radicals than necessary relative to the amount of methane will only result in the generation of unnecessary chlorine molecules.

[0067] Furthermore, there is an upper limit to the solubility of chlorine dioxide in water, and if the amount of chlorine dioxide increases beyond the upper limit of solubility, chlorine dioxide will be generated in the gas phase, increasing the risk of flammability. Therefore, it is preferable to determine the supply timing and supply amount of the sodium chlorite aqueous solution based on at least one of the amount of methane supplied to the reactor and the amount of chlorine dioxide present.

[0068] [Decision on additional supply of precursors] A method for determining the timing and amount of supply of the sodium chlorite aqueous solution will be described. The first method is to set a sodium chlorite additional supply plan based on the amount of methane present. Information regarding the amount of methane present is sent to the reactor 100 during or before the process in the reactor 100. The amount of methane present is calculated by subtracting the amount of methane consumed from the amount of methane supplied. Information regarding the amount of methane supplied can be obtained, for example, from a methane concentration detector installed in a methane supply pipe connected to the reactor 100 or from an estimated value of the amount of methane generated at the methane source. The additional sodium chlorite supply plan may be set by adding the amount of methane to be supplied in the future (supply plan) as the amount of methane present in the future. Information regarding the amount of methane consumed can be detected, for example, by a pressure detector 33 (see FIG. 1 or FIG. 4 described below) that detects the pressure inside the reaction vessel. This is because, as methane is consumed and liquefied into formic acid or methanol, the amount of methane contained in the gas layer S3 also decreases, and the pressure of the gas layer S3 decreases. This is because the degree of pressure decrease in the gas layer S3 correlates with the amount of methane consumed. A methane concentration detector and a pressure detector that detects the pressure inside the reaction vessel are also included in the "other sensors" mentioned above. A value corresponding to the future supply amount (supply plan) of methane to be supplied may be set as the future methane consumption amount. The reaction apparatus 100 derives the optimal additional supply amount of aqueous sodium chlorite solution for that supply amount from the amount of methane present, thereby formulating an additional supply plan for sodium chlorite and executing the additional supply plan.

[0069] The second method is to set a sodium chlorite supplemental supply plan based on the amount of chlorine dioxide present. The amount of chlorine dioxide present can be obtained using a chlorine dioxide concentration detector 13 (see FIG. 1 or FIG. 4 described below). The concentration detector 13 may include, for example, a light-receiving unit that detects transmitted or reflected light from the first solution S1. As a specific example, the concentration detector 13 may include, for example, a light-transmitting unit that emits visible light to the first solution S1 and a light-receiving unit that detects the color of light reflected by or transmitted through the first solution S1, and the amount of chlorine dioxide contained in the first solution S1 is estimated based on the intensity of the color. Because chlorine dioxide reflects yellow light in the first solution S1, the chlorine dioxide concentration (amount of chlorine dioxide present) can be obtained by detecting the intensity of the yellow light with a light-receiving unit (e.g., an image sensor). Alternatively, the amount of chlorine dioxide present may be predicted from the concentrations of each component of the mixed solution, the amount of methane supplied, the intensity of light L1, etc., and a sodium chlorite supplemental supply plan may be set based on the predicted amount present. The concentration of chlorine dioxide may be determined not only by the color depth but also by detecting other physical properties of chlorine dioxide.

[0070] 4 is a control block diagram of the reaction apparatus 100. A control unit 15 of the reaction apparatus 100 controls the light source 4, the power source 6 for the stirrer 5, the gas phase component supply pump 9, the methane supply valve 10, and the precursor supply pump 12. The control unit 15 is also connected to a concentration detector 13 and a pressure detector 33. The control unit 15 has an arithmetic unit 16 and a memory unit 17 therein.

[0071] An example of control of the reaction apparatus 100 when the first method (a method of setting an additional supply plan of sodium chlorite based on the amount of methane present) is adopted will be described. The memory unit 17 includes a table including the amount of methane present calculated using the pressure detector 33 or the like and the optimal additional supply amount of aqueous sodium chlorite solution for that amount, or an algorithm or function capable of estimating the optimal additional supply amount of aqueous sodium chlorite solution based on the amount of methane present. The control unit 15 is electrically connected to an external device of the reaction apparatus 100. The control unit 15 receives information regarding the amount of methane present from the external device. The calculation unit 16 estimates the optimal additional supply amount of aqueous sodium chlorite solution for the amount of methane present using the received information regarding the amount of methane present and the table, algorithm, or function stored in the memory unit. This process is repeated at regular or irregular intervals. In this manner, an additional supply plan of sodium chlorite is formulated.

[0072] An example of control of the reaction apparatus 100 when the second method (a method of setting an additional supply plan of sodium chlorite based on the amount of chlorine dioxide present) is adopted will be described. The control unit 15 receives information on the amount of chlorine dioxide present detected by the concentration detector 13. The memory unit 17 includes a table containing the amount of chlorine dioxide present and the amount of additional supply of sodium chlorite aqueous solution optimal for that amount, or an algorithm or function capable of estimating the amount of additional supply of sodium chlorite aqueous solution based on the amount of chlorine dioxide present. The calculation unit 16 uses the received information on the amount of chlorine dioxide present and the table, algorithm, or function stored in the memory unit 17 to estimate the amount of additional supply of sodium chlorite aqueous solution based on the amount of chlorine dioxide present. This is repeated at regular or irregular intervals. In this manner, an additional supply plan of sodium chlorite is formulated.

[0073] The control unit 15 operates the precursor supply pump 12 to supply sodium chlorite to the reaction vessel in accordance with the formulated additional supply plan for sodium chlorite. The precursor supply pump 12 can control the amount of aqueous sodium chlorite solution supplied per unit time. Although the reaction apparatus 100 of this embodiment includes the precursor supply unit 11, the reaction apparatus 100 does not necessarily have to include the precursor supply unit 11 itself. The reaction apparatus 100 has a connection port connected to the precursor supply unit 11, and may be connected to the precursor supply unit 11 external to the reaction apparatus 100 via the connection port.

[0074] [Stir bar] FIG. 5 is a cross-sectional view taken along a horizontal plane intersecting the stirrer 5. As shown in FIGS. 1 and 6, the reaction apparatus 100 includes the stirrer 5 and a power source 6 for the stirrer 5. In this embodiment, an electromagnetic coil is used as the power source 6, and a magnetic material is used for the stirrer 5. The stirrer 5 is disposed inside the reaction vessel, particularly near the bottom of the main body 1. A method in which the power source 6, such as a motor, is disposed above the reaction vessel and the stirrer 5 disposed inside the reaction vessel is rotated allows for accurate rotation with a simple structure. However, in a configuration in which a reaction in a closed system is preferred to reduce the risk of explosion, etc., it is advantageous to supply power to the stirrer 5 without contact.

[0075] Therefore, in this embodiment, the power source 6 uses multiple electromagnetic coils arranged outside the reaction vessel to rotate the stirrer 5, which is not in physical contact with the power source 6. The power source 6 is controlled by the control unit 15. Rotation of the stirrer 5 causes the interface BS between the layer of the first solution S1 and the layer of the second solution S2 to flow, accelerating the chemical reaction. Furthermore, as shown in FIG. 1 , stirring causes granular matter of the first solution S1 to form in the layer of the second solution S2, increasing the area of ​​the interface where the first solution S1 and the second solution S2 contact, accelerating the chemical reaction. However, to increase the amount of granular matter in order to increase the area of ​​the interface, the rotation speed of the stirrer 5 must be increased, resulting in increased power consumption by the power source 6. On the other hand, as the amount of granular matter increases, the effect of increasing the interface area decreases. Therefore, there is a limit to how much the rotation speed of the stirrer 5 can be increased to increase the amount of granular matter and efficiently carry out the chemical reaction. Therefore, in order to promote the chemical reaction, it is appropriate to maintain the interface BS without excessive stirring, to cause the interface BS to flow appropriately through stirring, and to cause the granular matter of the first solution S1 to appear appropriately.

[0076] The control unit 15 may change the rotation speed of the stirring bar 5 or rotate it intermittently. Furthermore, the control unit 15 may rotate the stirring bar in accordance with the additional supply of the sodium chlorite aqueous solution, or may rotate the stirring bar based on the amount of chlorine dioxide present detected by the concentration detector 13.

[0077] The stirrer 5 provided in the reaction apparatus 100 has been described above, but the characteristics of the stirrer 5 can also be applied to the stirrer 5 in the recovery tank 24 described later.

[0078] [Reaction vessel] The internal space of the reaction vessel has a cylindrical shape. There is no particular restriction on the volume of the internal space, but for example, it is 1 liter (0.001 m 3 ) or more, and 1000 liters (1 m 3The total amount of the mixed solution (first solution S1 and second solution S2) to be put into the reaction vessel is preferably 20 vol% or more and 90 vol% or less of the volume of the internal space, and more preferably 50 vol% or more and 70 vol% or less.

[0079] [Spout part] The reactor 100 includes, from bottom to top, a second solution S2, a first solution S1, and a gas layer S3 inside the reaction vessel. The gas layer S3 includes not only a layer composed of gaseous components but also a layer containing droplets or aerosols in the gas. The gas layer S3 may contain methane, a solute component of the second solution S2. The reactor 100 is equipped with a bubble generator. The bubble generator includes an inlet 18 for introducing gas (especially methane gas) from the gas layer S3, a pipe 19 connected to the inlet 18, a gas component supply pump 9 connected to the pipe 19 for supplying the gas from the gas layer S3 to the second solution S2, and a jet unit 8 for jetting the components of the gas layer S3 into the second solution S2. The gas component supply pump 9 is operated to introduce methane from the gas layer S3 through the inlet 18 and jet the methane from the jet unit 8 located near the bottom of the main body 1. As the bubbles containing methane pass through the second solution S2, the methane is further dissolved in the second solution S2.

[0080] The jetting part 8 has many fine jetting holes and generates small-diameter bubbles. The smaller the diameter of the bubbles, the better. In the case of bubbles called microbubbles, which have an average diameter of 1 μm or more and 100 μm or less, it may be possible to dissolve the gas in the gas layer S3 in the second solution S2 to a supersaturated state. Ultrafine bubbles with an average diameter of less than 1 μm may also be generated.

[0081] The pipe 19 is connected to a methane supply source 50 via a methane supply valve 10. As the chemical reaction progresses, the content of the non-polar solute (methane) in the reaction vessel decreases. In such a case, the methane supply valve 10 is opened to supply additional non-polar solute (methane) into the reaction vessel. As the methane is consumed, the pressure in the reaction section decreases. The pressure may be monitored by a pressure detector 33 to control the amount of methane supplied.

[0082] [Variations of control] Although the reactor 100 having the control unit 15 therein has been described above, the control unit 15 may exist independently of the reactor 100. The reactor 100 and the external control unit 15 may be electrically connected, and the control unit 15 may remotely control the reactor 100, or one control unit may operate multiple reactors 100. The calculation unit or memory unit may also exist independently of the reactor 100. For example, a general-purpose computer may be connected to the reactor 100, and the calculation unit and memory unit within the general-purpose computer may be used as the calculation unit and memory unit of the reactor 100.

[0083] Although the above describes an example in which the reactor 100 automatically controls the amount of precursor supplied from the precursor supply unit 11, the reactor may not have such automatic control. For example, an operator obtains information regarding the amount of methane gas present or detects the amount of chlorine dioxide present. Next, the operator calculates the timing and amount of precursor supply, inputs the information regarding the timing and amount of supply into the reactor, and stores it in the memory unit 17. The control unit 15 of the reactor drives the precursor supply pump 12 based on the information. The reactor may be one that enables such a process.

[0084] [light source] Chlorine dioxide (ClO2) exhibits high absorbance at 360 nm. Therefore, it is preferable to use light having a wavelength of 360 nm as light L1 for generating chlorine radicals from chlorine dioxide. In particular, it is preferable to use a light source having a dominant wavelength of 300 to 380 nm. As the light source 4 that emits light in this wavelength range, for example, an LED light source having a dominant wavelength of 356 nm can be used. In this specification, the dominant wavelength of the light source refers to the wavelength with the highest intensity in the emission spectrum of the light source. The light source is not limited to an LED light source, and may be another solid-state light source such as an LD, or a discharge lamp.

[0085] The number of light sources 4 is not particularly limited. In addition, Fig. 1 shows a state in which the light source 4 is disposed outside the reaction vessel and light L1 is introduced into the reaction vessel via a light guide 3 provided in the housing of the reaction vessel. However, the light source 4 may be disposed inside the reaction vessel, or the light source 4 may be incorporated into the wall of the reaction vessel.

[0086] In this embodiment, the two light sources 4 are the same type of light source, but different types of light sources may be combined. One may be a light source intended to generate chlorine radicals from chlorine dioxide, and the other may be a light source intended to generate chlorine radicals from chlorine molecules. As described above, chlorine molecules may be formed from chlorine radicals. However, by using a light source emitting light including 325 nm, which shows high absorbance to chlorine molecules, the chlorine molecules can be converted back to chlorine radicals. As such a light source, it is preferable to use a light source with a dominant wavelength of 305 to 345 nm. Furthermore, chlorine molecules may combine with water to generate hypochlorous acid (HClO). A light source intended to generate chlorine radicals from hypochlorous acid may also be used. By using a light source emitting light including 254 nm, which shows high absorbance to hypochlorous acid, chlorine radicals can be generated from hypochlorous acid. In this way, in addition to a light source intended to generate chlorine radicals from chlorine dioxide, a light source intended to generate chlorine radicals from other molecules may also be selected.

[0087] The light source 4 may be controlled in an intermittent lighting mode in which it is repeatedly turned on and off. The intermittent lighting mode allows for more efficient use of non-polar solutes and polar solutes in the reaction vessel. Regarding the interval between turning on and off the light source 4, for example, it may be turned on and off repeatedly at regular intervals. The lighting time may be 5 to 60 seconds, or 10 to 20 seconds. The lighting time may be 5 to 60 seconds, or 10 to 20 seconds. The lighting time and the lighting time may be the same.

[0088] [Light guide section] The light guide 3 is held by a mount that supports the light guide 3. The mount is fitted into an opening provided in the side wall of the reaction vessel. The light guide 3 may be made of a glass rod or an optical fiber. The position of the light guide 3 is not limited to the position shown in FIG. 1, and may be any of the upper part of the side wall, the lid, or the bottom of the reaction vessel.

[0089] [Reflective film] The reflective film will now be described in detail. Light reflected by the reflective film 7 illuminates the target again, improving the photoreaction efficiency. The reflective film 7 is preferably made of a material that is highly corrosion-resistant to the liquid in the reaction vessel. If a highly corrosion-resistant material is not used, a highly corrosion-resistant light-transmitting material may be provided on the surface of the reflective film 7. For example, an aluminum-based material is used for the reflective film 7 in this embodiment. Aluminum-based materials may not be sufficiently corrosion-resistant to chlorine-based substances (chlorine dioxide and chlorine radicals). Therefore, in this embodiment, an aluminum-based material is vapor-deposited on the outside of the glass vessel, and the vapor-deposited surface is protected with glass to prevent the aluminum-based material from coming into contact with the liquid in the reaction vessel. Note that if the inner wall of the reaction vessel itself reflects light L1, the reflective film 7 need not be formed. The reflective film 7 may be provided on the inner surface of the lid 2. However, a reflective surface is not an essential component.

[0090] Second Embodiment A second embodiment of the reaction apparatus will be described with reference to Fig. 6. Features different from the first embodiment will be mainly described, and features common to the first embodiment will not be described in principle. The same applies to the third and subsequent embodiments.

[0091] The reactor 200 comprises a vertically elongated cylindrical reaction vessel (1, 2) disposed at an incline. The bottom surface 61 of the reaction vessel body 1 is inclined relative to the horizontal plane h1. Even within the inclined reaction vessel (1, 2), a layer structure is formed, consisting of a layer of the first solution S1, a layer of the second solution S2, and a gas layer S3 in a third space not occupied by the first solution S1 and the second solution S2. Compared to an upright reaction vessel, the inclined reaction vessel has a larger interface area BS1 between the layer of the first solution S1 and the layer of the second solution S2, and a larger interface area BS2 between the layer of the first solution S1 and the gas layer S3. This promotes interfacial reactions within the reaction vessel. Furthermore, although the light source 4 is disposed near the sidewall of the body 1, because the reaction vessel is disposed at an incline, the light source 4 is positioned below the reaction vessel. While the lid 2 of the reaction vessel is not shown in FIG. 6, the reaction vessel has a lid 2 for supplying reactants into the reaction vessel.

[0092] In this embodiment, the stirrer 5 is physically connected to a power source 6 disposed outside the main body 1 of the reaction vessel by a rod 34 that transmits rotation. The extension direction of the rod 34 coincides with the axial direction of the rotation axis x1 of the stirrer 5. The angle t1 between the axial direction of the rotation axis x1 and any direction including the horizontal plane h1 is preferably 45 degrees or less, more preferably 35 degrees or less. This makes it easy for the stirrer 5 to be positioned across the layers of the first solution S1, the second solution S2, and the gas layer S3 (the layer in the third space in the reaction vessel that is not occupied by the layers of the first solution S1 and the second solution S2). As a result, when the stirrer 5 is rotated using the power source 6, the components of the first solution S1, the second solution S2, and the gas layer S3 are more thoroughly mixed together. In particular, the components of the gas layer S3 dissolve in the components of the second solution S2, increasing the contact area between the solutions. 12, the second solution S2 and the gas layer S3 appear in the form of particles in the first solution S1, the first solution S1 and the gas layer S3 appear in the form of particles in the second solution S2, and the first solution S1 and the second solution S2 appear in the form of particles in the gas layer S3. In particular, it is a great advantage to dissolve the components of the gas layer S3 into the layer of the second solution S2.

[0093] Note that arranging the stirrer 5 across multiple layers is one way to thoroughly stir the contents of the reaction vessel (the components contained in the first solution S1, the components contained in the second solution S2, and the components contained in the gas layer S3 of the third space), but this arrangement is not essential. For example, the contents of the reaction vessel can be stirred even when the stirrer 5 is arranged so as to be present within one layer.

[0094] The contents of the reaction vessel may be stirred by a method other than using the stirrer bar 5. For example, the reaction vessel may be continuously moved. Continuously moving the reaction vessel includes, for example, rotating, rocking, or vibrating the reaction vessel in order to stir the contents of the reaction vessel. Note that when the reaction vessel is moved from one location to another, the reaction vessel may be temporarily moved, and the contents of the reaction vessel may be stirred while being moved, but the relocation of the reaction vessel is not included in "continuously moving."

[0095] The reaction apparatus 200 may have a power source for continuously moving the reaction vessel. If the reaction vessel has a protruding piece that partially protrudes inward from the inner wall, the contents collide with the protruding piece when the reaction vessel is continuously moved, making it easier to agitate the contents. Alternatively, instead of vibrating the reaction vessel, the contents of the reaction vessel may be agitated by forcefully supplying the contents into the reaction vessel or by vibrating the contents themselves.

[0096] Third Embodiment A third embodiment of the reactor will be described with reference to FIG. 7. The reactor 300 differs from the reactor 100 of the first embodiment and the reactor 200 of the second embodiment in that the location where the first solution S1 and the second solution S2 are mixed to produce a mixed liquid and the location where the mixed liquid is irradiated with light are different. The location where the mixed liquid is produced is the mixing section 22, and the location where the mixed liquid is irradiated with light is the light irradiation section 21. The light irradiation section 21 is located downstream of the mixing section 22, and the mixing section 22 is located upstream of the light irradiation section 21. It is preferable that no other functional section is interposed between the mixing section 22 and the light irradiation section 21. The mixing section 22 and the light irradiation section 21 are connected by piping. It is preferable that the piping between the mixing section 22 and the light irradiation section 21 is as short as possible, and the distance between the mixing section 22 and the light irradiation section 21 is preferably within 1 m, and more preferably within 500 mm.

[0097] [Mixing section] FIG. 8 is an enlarged view of the mixing unit 22. The mixing unit 22 has a structure in which the second solution S2 is ejected from a thin tube in a narrow channel where the inner diameter of the first solution S1 is reduced. The internal pressure of the first solution S1 increases in the narrow channel portion. The second solution S2 is ejected into the increased internal pressure. For ease of understanding, the second solution S2 is depicted in the figure as a small droplet, but it is not necessarily in a small droplet form. Immediately after ejection, the first solution S1 and the second solution S2 are not completely mixed. When the first solution S1 and the second solution S2 move from the narrow channel portion to the wide channel portion, the internal pressure drops rapidly, causing turbulence in the first solution S1 and the second solution S2. This turbulence allows the first solution S1 and the second solution S2 to mix well. In this way, the mixing unit 22 adjusts the flow rate and pressure of the fluids to mix them.

[0098] In this embodiment, the mixing section 22 is arranged so that the direction of fluid flow is horizontal; however, the mixing section 22 may be arranged so that the direction of fluid flow is vertical (from bottom to top, or from top to bottom). The region where the inner diameter of the mixing section 22 changes may be tapered. Instead of inserting the second solution S2 into the flow of the first solution S1 as shown in FIG. 8, a configuration in which the first solution S1 is inserted into the flow of the second solution S2 may be used. Furthermore, the mixing section 22 is not limited to the type shown in FIG. 8, and various configurations of mixing sections may be applied. For example, a mixing section in which one liquid flows in a spiral shape and another liquid flows that interferes with the spiral flow may be used.

[0099] [Light irradiation unit] 9 is an enlarged view of the light irradiation unit 21. A mixed solution (S1+S2) of the first solution S1 and the second solution S2 mixed in the mixing unit 22 is irradiated with light L1 from a light source 4 outside the piping, so that the mixed solution (S1+S2) passes through an irradiated area 35. A light transmission unit 36 ​​is located between the light source 4 and the irradiated area 35. The light transmission unit 36 ​​may be made of a material that has a high transmittance to the dominant wavelength of the light source 4, such as quartz glass.

[0100] A first advantage of this embodiment is that there is no gas layer in the irradiated region 35. The target to be irradiated is the interface between the first solution S1 and the second solution S2, not the gas layer S3. Because there is no gas layer S3, light L1 is not irradiated to the gas layer S3, and more light is irradiated to the interface between the first solution S1 and the second solution S2. This allows light L1 to be used more efficiently in the photochemical reaction that generates chlorine radicals. A second advantage of this embodiment is that the first solution S1 and the second solution S2 are more easily mixed in the mixing section 22, and there are more interfaces between the two solutions. Because there are more interfaces, the generated chlorine radicals are more likely to come into contact with methane. As a result, the chemical reaction can be carried out efficiently.

[0101] The light irradiation unit 21 shown in Figure 9 has one light source 4. The light source 4 has a plurality of small light sources (individually LEDs) 4a, a board 4b on which the plurality of small light sources 4a are arranged, and a stand 4c that holds the board 4b. In this embodiment, one stand 4c holds one board 4b, but one stand 4c may also hold a plurality of boards 4b. The stand 4c functions as a heat sink to suppress heat generation from the light source.

[0102] In this specification, when a light source is composed of an array of small light sources such as LEDs, the number of light sources is counted by counting the number of stands 4c that hold the substrates 4b. For example, if there are two stands 4c, the number of light sources 4 is considered to be two.

[0103] [Recovery tank] Returning to FIG. 7, the description of the reaction apparatus 300 will be continued. In the light irradiation unit 21, the flowing mixed solution (S1+S2) passes through the irradiated area 35, so not all of the chlorine dioxide in the mixed solution (S1+S2) is converted to chlorine radicals in one pass through the irradiated area 35. Chlorine dioxide remains in the mixed solution that leaves the light irradiation unit 21. The mixed solution (S1+S2) containing the remaining chlorine dioxide is transported to the recovery tank 24 by the pump 26. In the recovery tank 24, the mixed solution (S1+S2) is kept stationary, so the mixed solution (S1+S2) separates into a layer of the first solution S1 and a layer of the second solution S2. At this time, the methanol and formic acid produced by the series of chemical reactions are contained in the first solution S1.

[0104] The recovery tank 24 has an outlet 24a for discharging the layer-separated first solution S1 and an outlet 24b for discharging the layer-separated second solution S2. Although not shown, the outlets 24a and 24b are each equipped with an on-off valve that can open and close the opening of the outlet. After layer separation, the first solution S1 discharged from the outlet 24a is guided back to the mixing section 22 using a pump or the like (not shown). The second solution S2 discharged from the outlet 24a is guided to the second solution tank 23.

[0105] The second solution tank 23 contains a layer of the second solution S2 and a gas layer S3. Methane (a non-polar solute) in the gas layer S3 is sucked in by the pump 27 and bubbled into the second solution S2, dissolving the methane in the gas layer S3 in PFO (a non-polar solvent). If additional methane can be supplied, the methane supply valve 10 is opened to supply methane from the methane supply source 50. The methane-containing PFO solution (second solution S2) obtained in this manner is introduced back into the mixing section 22 using a pump (not shown) or the like.

[0106] The mixed solution (S1+S2) mixed again in the mixer 22 is again irradiated in the light irradiator 21, where chlorine radicals are generated from the chlorine dioxide remaining in the mixed solution (S1+S2) and bonded with methane. In this way, the first solution S1 and the second solution S2 are circulated in the reaction device 300, and methane is converted into methanol and formic acid.

[0107] The recovery tank 24 is equipped with a concentration detector 13. Chlorine dioxide, a polar solute, is yellow in aqueous solution. Therefore, the color of the recovered first solution S1 is detected. A dark yellow color indicates a high concentration of chlorine dioxide in the first solution S1, and a light yellow color indicates a low concentration of chlorine dioxide in the first solution S1.

[0108] A decrease in the chlorine dioxide concentration in the first solution S1 indicates that methanol and formic acid are produced in the first solution S1. Therefore, when the control unit 15 determines that the yellow color is light based on the detection result of the concentration detector 13, it opens the precursor on-off valve 32 and supplies the precursor (sodium chlorite aqueous solution) from the precursor supply unit 11.

[0109] After a long period of operation of the reactor, if it is assumed that the concentrations of formic acid and methanol have been sufficiently secured, the precursor on-off valve 32 is kept closed to promote the reaction of the remaining chlorine dioxide for a sufficient time until all the chlorine dioxide is used up.

[0110] Thereafter, the discharge valve 28 connected to the recovery tank 24 for discharging the first solution S1 is opened, and the first solution S1 containing the products, methanol and formic acid, is extracted into the extraction tank 25.

[0111] If a polar solvent such as water is insufficient for the next treatment, the polar solvent may be additionally supplied from an inlet (not shown) to the collection tank 24. If a nonpolar solvent such as PFO is insufficient, the nonpolar solvent may be additionally supplied from an inlet (not shown) to the collection tank 24 or the second solution tank 23.

[0112] <Fourth embodiment> A fourth embodiment of the reactor will be described with reference to Fig. 10. Similar to the reactor 300 of the third embodiment, the reactor 400 also has the mixing section 22 and the light irradiation section 21 disposed in different locations and connected to each other by a pipe. The light irradiation section 21 is located downstream of the mixing section 22.

[0113] In the reaction apparatus of this embodiment, the polar solutes in the mixed solution (S1 + S2) are not consumed in multiple circulations as in the third embodiment, but are instead consumed almost entirely in a single circulation. Therefore, the irradiated region 35 of the light irradiation unit 21 in this embodiment is sufficiently long. The concentration of the polar solute (chlorine dioxide) contained in the mixed solution (S1 + S2) discharged from the light irradiation unit 21 is preferably low enough that further light irradiation does not efficiently generate activated species. The mixed solution (S1 + S2) discharged from the light irradiation unit 21 is supplied to the second solution tank 23 and the recovery tank 24 using a pump 26. The supply ratio to the second solution tank 23 and the recovery tank 24 can be appropriately adjusted using a flow control valve (not shown).

[0114] In the second solution tank 23, a non-polar solute (methane) is additionally supplied to the mixed solution (S1+S2) from a methane supply source 50. Since the second solution tank 23 has an outlet disposed at the bottom of the tank, the liquid rich in the second solution S2, which contains a large amount of non-polar solute, can be preferentially discharged.

[0115] When the supply of liquid and stirring are stopped and the collection tank 24 is allowed to stand, the mixture (S1 + S2) separates into layers. This separation allows the first solution S1, containing the product methanol and formic acid, to be extracted into the extraction tank 25. After the extraction, the collection tank 24 contains the first solution S1, but a liquid rich in the second solution S2 remains. In this state, the precursor on-off valve 32 is opened, a precursor (aqueous sodium chlorite solution) is supplied from the precursor supply unit 11, and the collection tank 24 is stirred with the stirrer 5. This produces a mixture (S1 + S2) in which a small amount of the first solution S1, containing a large amount of polar solute (chlorine dioxide), exists in the form of particles in the second solution S2. Because the collection tank 24 has an outlet located at the bottom of the tank, the mixture (S1 + S2) rich in the second solution S2, in which a small amount of the first solution S1, containing a large amount of polar solute (chlorine dioxide), exists as tiny solution particles in the second solution S2, can be preferentially discharged.

[0116] In this embodiment, a sprinkler nozzle 31 is used to supply the solution to the collection tank 24. By using the sprinkler nozzle 31 to supply the solution in the form of droplets to the collection tank 24, when the collected mixed solution (S1+S2) passes through the first solution S1, the polar solutes in the first solution S1 are more likely to come into contact with the mixed solution (S1+S2), and the products (methanol and formic acid) in the mixed solution (S1+S2) are more likely to come into contact with the first solution S1. When the contents in the collection tank 24 are allowed to stand and the layers are separated, the layers can be separated so that the appropriate substances are located in the appropriate layers. The stirrer 5 is also used for the same purpose.

[0117] In the mixer 22, a second solution S2-rich mixture (S1+S2) from the recovery tank 24, which has dissolved therein minute polar solution bubbles containing a large amount of polar solutes, is mixed with a second solution S2-rich mixture from the second solution tank 23, which contains a large amount of non-polar solutes. The mixture thus mixed is a mixture (S1+S2) that contains a large amount of polar solutes and non-polar solutes but is mainly composed of the second solution S2. This mixture is then sent back to the light irradiation unit 21.

[0118] Fifth Embodiment A fifth embodiment of the reactor will be described with reference to FIG. 11. Similar to the fourth embodiment, the fifth embodiment is configured to consume most of the polar solute in the mixed solution (S1+S2) in one circulation. The light irradiation unit 21 of the reactor 500 of the fifth embodiment is equipped with two light sources. The two light sources are connected in series, thereby expanding the irradiated area 35. The two light sources may also be connected in parallel.

[0119] After being discharged from the light irradiation unit 21, the mixed solution (S1+S2) enters the product trap 29. Water S4 is stored in the product trap. The products (methanol and formic acid) contained in the mixed solution (S1+S2) dissolve in the water, and the products are trapped. Note that if a small amount of polar solute (chlorine dioxide) remains, the polar solute is also trapped in the water. As in the fourth embodiment, the liquid (substantially only the second solution S2) that leaves the product trap 29 is supplied to the second solution tank 23 and the recovery tank 24 using the pump 26.

[0120] The above describes the embodiments and their modifications of the method for chemically reacting a polar solute and a non-polar solute. The above embodiments and their modifications merely illustrate examples of the present invention, and the present invention is not limited to the above embodiments and their modifications. Various changes or modifications can be made to the above embodiments and their modifications, and the above embodiments or their modifications can be combined, without departing from the spirit of the present invention.

[0121] In this specification, a location where there is an on-off valve but no pump upstream or downstream thereof is a location where the inlet pressure of the on-off valve can be set to be higher than the outlet pressure, and liquid can flow out simply by opening the on-off valve without using a pump. A pump may be used instead of an on-off valve where an on-off valve is used. Conversely, a on-off valve set so that the inlet pressure is higher than the outlet pressure may be used instead of a pump where a pump is used. Gravity may be used to make the inlet pressure higher than the outlet pressure. Of course, an on-off valve and a pump may be used together.

[0122] In the above embodiment, the case where an aqueous solution containing chlorine dioxide and a solution containing a non-polar solvent containing methane is used has been described. This combination of substances is only an example, and the above-described reaction apparatus and chemical reaction method can also be applied to cases where other polar solutions or other non-polar solutions are used.

[0123] For example, in the example described in Patent Document 1, an ethanol solution containing metal ions may be used as the polar solution, and hexane containing dioxins may be used as the non-polar solution. In this case, since the specific gravity of the non-polar solution is smaller than that of the polar solution, the non-polar solution will form an upper layer and the polar solution will form a lower layer.

[0124] In the reaction apparatus of each of the above embodiments and their modifications, the main body 1 of the reaction vessel may be provided with liquid level lines that serve as a guide for the supply amounts of the first solution S1 and the second solution S2. The supply amounts of the first solution S1 and the second solution S2 to the reaction vessel may be set, and the supply amounts may be clearly indicated in the instruction manual of the reaction apparatus, etc. A reaction apparatus having these features means that the height of the interface BS between the first solution S1 and the second solution S2 and the height of the interface between the second solution S2 and the gas layer S3 are set. Furthermore, substances that can be used as the first solution S1 and the second solution S2 may be clearly indicated on the housing of the reaction vessel or in the instruction manual of the reaction apparatus, etc. [Example]

[0125] The following experiments were carried out using the reaction apparatus 600 shown in Fig. 12. The common experimental conditions were as follows:

[0126] [Common conditions for the experiment] The common conditions for the main experimental conditions are described below. Reactor 600: A type similar to the reactor 200 of the second embodiment in which the main body 1 of the reaction vessel is arranged at an angle. The volume of the reaction vessel is 600 cc. Light source 4: One LED light source with a dominant wavelength of 365 nm, irradiated from the bottom of the reaction vessel. Irradiation is not intermittent, but is continuously lit. Stirring bar 5: Stirring bar having a rod 34. The rotation speed is 180 rpm to 360 rpm, and the bar rotates intermittently by repeating rotation on for 5 seconds and rotation off for 20 seconds. First solution S1: 50 cc of chlorine dioxide aqueous solution, chlorine dioxide concentration 100 mM. Second solution S2: 250 cc of methane-containing PFO solution, methane concentration 15 mM. Layer S3: 100% methane gas.

[0127] Experiments were carried out on the two samples under different conditions as follows. [Sample 1] After the reaction started, sodium chlorite (concentration: 2.5M) was added dropwise from precursor supply unit 11 using precursor supply pump 12 to maintain the chlorine dioxide concentration at 100mM. The total amount of sodium chlorite added after the reaction started was equivalent to a chlorine dioxide concentration of 200mM. In other words, the total amount of chlorine dioxide used in the experiment reached 300mM. After the lamp was turned on for a certain period of time, the products (methanol and formic acid) were extracted from the contents, and the concentration of the products in the contents was determined to be 74.4mM. [Sample 2] After the reaction started, nothing was supplied from the precursor supply unit 11. In other words, the total amount of chlorine dioxide used in the experiment was 100 mM. After the light was turned on for a certain period of time, the products (methanol and formic acid) were extracted from the contents, and the concentration of the products in the contents was determined to be 18.2 mM.

[0128] [Analysis of experimental results] Methane Conversion Efficiency (MCE) was used as an index of reaction efficiency. MCE can be calculated by dividing the molar concentration of the products (formic acid and methanol) by the total molar concentration of chlorine dioxide. MCE of sample 1: 74.4 mM / 300 mM ≒ 0.248 (24.8%) MCE of sample 2: 18.2 mM / 100 mM = 0.182 (18.2%) Since the MCE of Sample 1 was higher than that of Sample 2, it was found that Sample 1 was able to convert methane to formic acid and methanol more efficiently.

[0129] From another perspective, it can be said that Sample 1 used three times the amount of chlorine dioxide as Sample 2, and therefore if Sample 1 reached a product molar concentration of 54.6 mM, which is three times the product molar concentration of 18.2 mM in Sample 2, it could be said to have the same efficiency as Sample 2. However, the result was that the product was obtained in excess of the target of 54.6 mM by 19.8 mM. In this way, the experiment confirmed that the efficiency of the chemical reaction can be increased by additionally supplying sodium chlorite, a precursor to the polar solute. [Explanation of symbols]

[0130] 1: (Reaction vessel) body 2: (Reaction vessel) lid 3: Light guide section 4:Light source 5: Stirring bar 6: Power source (for stirring bar) 7: Reflective film 8: Spout part 9: Air layer component supply pump 10: Methane supply valve (non-polar solute supply valve) 11: Precursor supply section 12: Precursor supply pump 13: Concentration detector 15: Control section 16: Arithmetic section 17: Storage section 18:Intake port 19: Piping 34: Rod (transmits power to the stirrer) 50: Non-polar solute source (methane source) 61: Bottom 100, 200, 300, 400, 500, 600: Reactor BS, BS1, BS2: Interface L1: Light (emitted by a light source) S1: First solution S2: Second solution S3: Air layer

Claims

1. 1. A method for chemically reacting a polar solute with a non-polar solute, said method comprising: a method for irradiating a mixed solution obtained by mixing a first solution mainly containing a polar solute and a second solution mainly containing a non-polar solute with light from a light source, and additionally supplying a precursor of the polar solute based on a means for estimating at least one of the amount of the non-polar solute and the amount of the polar solute present using light reflected from the first solution, light transmitted through the first solution, or another sensor.

2. 10. The method of claim 1, wherein the molar concentration of the polar solute precursor fed is at least 10 times higher than the molar concentration of the polar solute produced.

3. The method according to claim 1, wherein a stirrer is provided in a container to which the precursor is additionally supplied, and the precursor is additionally supplied while being stirred using the stirrer.

4. 2. The method according to claim 1, wherein the container for additionally supplying the precursor is the same as the container containing the mixed solution and being irradiated with light.

5. The first solution and the second solution are mixed in a mixing section; The method according to claim 1, wherein the mixed solution mixed in the mixing section is irradiated with the light by a light irradiation section located downstream of the mixing section.

6. 6. The method according to claim 5, wherein the mixed solution after the light irradiation is recovered, the recovered mixed solution is separated into the first solution and the second solution, and the separated first solution and second solution are mixed again in the mixing section.

7. 7. The method according to claim 6, wherein the recovered mixture is separated into two layers in a recovery tank, and the first solution is extracted from the upper layer and the second solution is extracted from the lower layer.

8. 6. The method according to claim 5, wherein the recovered mixed solution is fed to a first liquid tank and a second liquid tank, a precursor of the polar solute is additionally supplied to the first liquid tank to form a new first solution, a precursor of the non-polar solute is additionally supplied to the second liquid tank to form a new second solution, and the new first solution and the new second solution are mixed again in the mixing section.

9. The method according to any one of claims 5 to 8, wherein the mixing section mixes the first solution and the second solution by spraying the other solution into a narrow channel that guides the other solution.

10. 1. An apparatus for chemically reacting a polar solute with a non-polar solute, the apparatus comprising: a light irradiation unit that irradiates a mixed solution obtained by mixing the first solution mainly containing the polar solute and the second solution mainly containing the non-polar solute with light from a light source; a precursor supply unit that additionally supplies a precursor of the polar solute; a detector that detects reflected light or transmitted light from the first solution using a light receiving unit or other sensor to estimate at least one of the amount of the non-polar solute and the amount of the polar solute; an arithmetic unit that determines the amount of the precursor to be supplied by the precursor supply unit based on at least one of the estimated amount of the non-polar solute and the estimated amount of the polar solute when generating the mixed solution containing the additionally supplied precursor.

11. The apparatus according to claim 10, wherein the container for additionally supplying the precursor also serves as a container to which light is irradiated from the light irradiating unit.

12. 12. The apparatus of claim 11, wherein the vessel for supplying additional precursor comprises a stir bar.

13. The device according to claim 10, further comprising a mixing section located upstream of the light irradiation section, for mixing the first solution and the second solution.

14. 14. The device according to claim 13, wherein the mixing section mixes the first solution and the second solution by spraying the other solution into a narrow channel that guides one of the first solution and the second solution.

15. 11. The device according to claim 10, further comprising at least one recovery tank for recovering the mixed liquid after light irradiation, wherein the light irradiation unit re-irradiates the mixed liquid recovered in the recovery tank with light.

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