Method for producing alkane oxide

Abstract

To provide a method for producing an alkane oxide that uses oxygen as an oxidizer at lower temperatures than in the conventional art.SOLUTION: A method for producing an alkane oxide includes the step of applying light, in an oxygen-containing atmosphere, to a reaction solution containing an alkane, an electron attractive group-bearing p-benzoquinone, a metal salt and water. The step has a reaction temperature that is 0°C or higher and lower than the boiling point of the solvent of the reaction solution. The metal salt includes a metal element that is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu. The wavelength band of the light includes the maximum absorption wavelength of the p-benzoquinone.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing alkane oxides.

Background Art

[0002] Among petroleum components, alkanes are effectively used as energy sources. However, alkanes are difficult to chemically change and are difficult to use as raw materials (reaction substrates) for chemical reactions. In addition, among alkanes, gaseous alkanes at normal temperature and pressure have a high cost burden for storage and transportation. Among such gaseous alkanes, methane also has an aspect as a greenhouse gas.

[0003] Therefore, conventionally, studies have been made to oxidize alkanes and use the obtained oxidation products as raw materials for chemical reactions.

[0004] In the following description, the oxidation products obtained by oxidizing alkanes are referred to as "alkane oxides". Examples of alkane oxides include alcohols, aldehydes, ketones, and peroxides. By the above reaction, the applications of alkanes can be expanded. In addition, gaseous alkanes at normal temperature and pressure are referred to as "gaseous alkanes". Examples of gaseous alkanes include methane, ethane, propane, and butane.

[0005] When gaseous alkanes are oxidized by the above oxidation reaction to obtain alkane oxides, the applications are expanded. In addition, many of the obtained alkane oxides are compounds that are liquid at normal temperature and pressure, making them easy to handle.

[0006] On the other hand, alkanes, especially gaseous alkanes, have a high C-H bond dissociation energy and often require high-temperature conditions or conditions using an oxidizing agent that is easy to react in the oxidation reaction. Therefore, in recent years, techniques for oxidizing alkanes near room temperature have been reported (for example, see Patent Document 1). In addition, techniques for oxidizing alkanes using oxygen as an oxidizing agent have been reported (for example, see Non-Patent Document 1).

Prior Art Documents

Patent Document

[0007]

Patent Document 1

Non-Patent Document

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in the method described in Patent Document 1, highly reactive hydrogen peroxide is used as an oxidizing agent. In the method described in Non-Patent Document 1, high-temperature conditions exceeding 100 °C are required as the reaction temperature. For example, in a low-temperature environment such as room temperature, a technique for oxidizing alkanes using oxygen as an oxidizing agent has not been put into practical use and improvement has been demanded.

[0010] The present invention has been made in view of such circumstances, and an object thereof is to provide a method for producing an alkane oxide using oxygen as an oxidizing agent in a lower-temperature environment than before.

Means for Solving the Problems

[0011] To solve the above problems, one aspect of the present invention includes the following aspects.

[0012] [1] A step of irradiating a reaction solution containing an alkane, para-benzoquinone having an electron-withdrawing group, a metal salt, and water with light in an oxygen-containing atmosphere, wherein the reaction temperature of the step is 0 °C or higher and lower than the boiling point of the solvent of the reaction solution, the metal element included in the metal salt is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu, and the wavelength band of the light includes the maximum absorption wavelength of the para-benzoquinone. A method for producing an alkane oxide.

[0013] [2] The production method of the alkane oxide according to [1], wherein the reaction solution further contains nitrite ions.

[0014] [3] The production method of the alkane oxide according to [1] or [2], wherein the para - benzoquinone is 2,3 - dichloro - 5,6 - dicyano - p - benzoquinone or tetrachloro - 1,4 - benzoquinone.

[0015] [4] The production method of the alkane oxide according to any one of [1] to [3], wherein the metal element is Cu.

[0016] [5] The production method of the alkane oxide according to [4], wherein the metal salt is copper acetate.

[0017] [6] The production method of the alkane oxide according to any one of [1] to [5], wherein the solvent of the reaction solution is acetonitrile.

[0018] [7] The production method of the alkane oxide according to any one of [1] to [6], wherein the reaction temperature is 10°C or higher and 40°C or lower.

[0019] [8] The production method of the alkane oxide according to any one of [1] to [7], wherein the alkane contains at least one selected from the group consisting of methane, ethane, propane, and butane. [Advantages of the Invention]

[0020] According to the present invention, a method for producing an alkane oxide using oxygen as an oxidant can be provided in a temperature environment lower than before. [Brief Description of the Drawings]

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0022] The method for producing alkane oxides according to this embodiment includes a step of irradiating a reaction solution containing an alkane, para-benzoquinone having an electron-withdrawing group, a metal salt, and water with light in an oxygen-containing atmosphere. In the method for producing alkane oxides of this embodiment, oxygen molecules contained in the atmosphere function as an oxidizing agent.

[0023] Here, the "oxidizing agent" in this embodiment refers to a compound that is reduced by receiving electrons taken from the reaction substrate through an oxidation reaction and has a function of moving them outside the reaction system. In that sense, oxygen molecules are reduced by receiving electrons taken from the reaction substrate through an oxidation reaction and move the electrons outside the reaction system in the form of water molecules. Details will be described later. The following will be described in order.

[0024] The "oxygen-containing atmosphere" refers to an environment containing oxygen in the atmosphere. Typically, it is under the atmosphere.

[0025] The reaction temperature of the process is 0 °C or higher and lower than the boiling point of the solvent of the reaction solution. It is preferable that the reaction temperature is near room temperature for easy management of the reaction conditions. Here, "room temperature" refers to 25 °C. The reaction temperature is preferably 5 °C or higher, more preferably 10 °C or higher. Also, the reaction temperature is preferably 50 °C or lower, more preferably 40 °C or lower. The upper limit value and the lower limit value of the reaction temperature can be arbitrarily combined.

[0026] In the present invention, the alkane as the reaction substrate may be liquid or gaseous under an atmospheric pressure and at room temperature environment. In the method for producing an alkane oxide of the present invention, gaseous alkane can also be preferably subjected to an oxidation reaction.

[0027] The alkane as the reaction substrate may contain gaseous alkane. That is, the alkane may contain at least one selected from the group consisting of methane, ethane, propane, and butane.

[0028] Para-benzoquinone having an electron-withdrawing group functions as an oxidation catalyst in the oxidation reaction. Examples of the electron-withdrawing group include a halogen atom and a cyano group. As such para-benzoquinone, 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or tetrachloro-1,4-benzoquinone (chloranil) is preferable.

[0029] In addition, it has been confirmed that when using para - benzoquinone (or hydroquinone) without an electron - withdrawing group, hydroquinone decomposes during the reaction.

[0030] The metal element contained in the metal salt is a first - row transition element and is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu. The metal element is preferably Cu. Since these metal elements have redox activity, it is considered that the oxidation reaction for the purpose described later proceeds.

[0031] On the other hand, for example, in the case of zinc (Zn) in which the metal element contained in the metal salt has redox inactivity, it is considered that the target oxidation reaction proceeds.

[0032] The anion contained in the metal salt is not particularly limited as long as it forms a metal salt soluble in the solvent described later. As the type of anion, nitrate ion (NO3 - ), acetate ion, perchlorate ion (ClO4 - ), and sulfate ion (SO4 2- ) are preferable, and acetate ion is more preferable. As the anion, chloride ion can also be used.

[0033] As the metal salt, for example, copper acetate (Cu(OAc)2) is preferable.

[0034] Note that the metal salt used may have water of hydration. For example, the above - mentioned copper acetate may be Cu(OAc)2·H2O containing water of hydration.

[0035] The solvent is a polar solvent that can dissolve alkane, para - benzoquinone, metal salt, and water, and is relatively less likely to be oxidized than the alkane which is the reaction substrate in the oxidation reaction. As such a solvent, acetonitrile can be preferably used.

[0036] When using a gaseous alkane as the alkane, the gaseous alkane exists in the gas phase of the reaction environment together with oxygen. When using acetonitrile as the solvent, the alkane in the gas phase can be preferably dissolved and used for the oxidation reaction.

[0037] Also, when the oxidation reaction of the present embodiment is carried out under a high-pressure environment, water can also be used as the solvent. Since water is less likely to undergo an oxidation reaction compared to the alkane, it is possible to suppress the problem that the solvent is oxidatively decomposed during the reaction.

[0038] In addition, since the solubility of the alkane in water is low, it is difficult for a sufficient amount of alkane to dissolve in the reaction solution at normal pressure, and the oxidation reaction hardly proceeds. Therefore, when using water as the solvent, it is advisable to promote the dissolution of the alkane from the gas phase into the solvent and advance the oxidation reaction by reacting under a high-pressure environment.

[0039] The wavelength band of the light irradiated on the reaction solution includes the maximum absorption wavelength of the para-benzoquinone used. By irradiating light of such a wavelength, para-benzoquinone absorbs and is excited by the irradiated light, and the oxidation reaction of the alkane described later can be advanced.

[0040] As the light to be irradiated, for example, visible light with ultraviolet light in the ultraviolet region cut off can be adopted. Such light can be adjusted by emitting light from a light source that emits light including visible light and passing the emitted light through a UV filter that cuts off ultraviolet light of 390 nm or less, for example.

[0041] The reaction solution preferably further contains nitrite ions (NO2 - ). Nitrite ions are considered to contribute to the catalytic cycle in the oxidation reaction. Therefore, the presence of nitrite ions in the reaction solution can promote the oxidation reaction of the alkane.

[0042] The concentration of nitrite ions can be controlled by adding nitrite such as NaNO2 to the reaction solution.

[0043] Figure 1 is a diagram showing the oxidation reaction of the present embodiment. In Figure 1, DDQ is used as para-benzoquinone. Also, the ligand (Ligand) indicated by L in Figure 1 can exemplify anions such as acetate ions and nitrite ions present in the reaction system, or water molecules that hydrate metal ions. The inventor considers the oxidation reaction of alkanes in the present embodiment as follows.

[0044] First, when the reaction solution is irradiated with light, DDQ becomes a chemical species (oxidation active species) in the triplet excited state ( 3 DDQ * ). The generated chemical species has a high reduction potential (E red = 3.18V vs SCE). Therefore, it is considered that the generated chemical species oxidizes the metal salt using the oxygen atom constituting the water molecule (symbol (II) in the figure). Specifically, in the reaction system, the metal salt receives the coordination of water molecules to form an aqua complex (LM n+ -OH2). The generated aqua complex is 3 DDQ * electron-transfer oxidized.

[0045] The chemical species (oxidation active species: LM n+ =O, or LM (n+2)+ -O (n+1)+ -O · ) generated by the oxidation of the metal salt-aqua complex reacts with the alkane in the system to oxidize the alkane (symbol (III) in the figure). On the other hand, when the chemical species donates an oxygen atom to the alkane and reacts with the water molecules in the system, the metal salt-aqua complex is regenerated.

[0046] On the other hand, the triplet excited state DDQ becomes a reduced form (DDQH2) by oxidizing the metal salt-aqua complex (symbol (IV) in the figure). The reduced form is oxidized by oxygen molecules (O2) in the system, and DDQ is regenerated. The oxygen molecules are reduced to water molecules and move out of the reaction system. The oxygen molecules function as an oxidizing agent in the oxidation reaction shown in Figure 1.

[0047] At this time, if nitrite ions are present in the system, nitrogen dioxide generated by the reduction of nitrite ions oxidizes DDQH2 and promotes the reaction to regenerate DDQ. Nitric oxide generated by oxidizing DDQH2 is oxidized by oxygen in the system to regenerate nitrogen dioxide (in the figure, symbol (V)). Oxygen molecules are reduced to water molecules and move outside the reaction system.

[0048] That is, it is considered that the oxidation reaction of the alkane in the present embodiment is contributed by the oxidation cycle A of the alkane by the chemical species generated by the oxidation of the metal salt-aqua complex and the regeneration cycle B of DDQ that oxidizes the metal salt-aqua complex.

[0049] In addition, other chemical species in the above reaction cycle are also considered to contribute to the reaction. A peroxy radical (ROO·) is generated by the combination of a radical (R·) generated from an alkane (R-H) and oxygen. It is also considered that the generated peroxy radical oxidizes the reduced form of DDQ and promotes the regeneration cycle B of DDQ. When the reaction product is analyzed, a peroxide (ROOH) of the alkane is detected as an alkane oxide, so it is considered that the above reaction also occurs.

[0050] The control factors of the above catalytic reaction can be explained as follows.

[0051] (Light intensity) As described above, the catalytic reaction occurring in the present invention of the application is triggered by the photoexcitation of DDQ. Therefore, the greater the light irradiation amount, the greater the triplet excited state of DDQ and the more the oxidation reaction is promoted.

[0052] (Oxygen concentration) In the above catalytic reaction, it is considered that oxygen molecules contribute to the oxidation reaction of the reduced form DDQH2 of DDQ and regenerate DDQ. Therefore, it is considered that as the amount of oxygen in the system increases, the regeneration cycle B of DDQ becomes easier to rotate and the oxidation reaction is promoted.

[0053] The oxygen concentration in the system can be controlled by controlling the partial pressure of oxygen in the gas phase.

[0054] (Water concentration) In the above catalytic reaction, alkanes are oxidized by oxygen atoms that make up water molecules in the system. Therefore, it is considered that as the molecular weight of water increases, the oxidation cycle A of alkanes becomes easier to rotate. On the other hand, if the water in the system increases too much, it is considered that each chemical species reacts with water and deactivates the reaction. Therefore, it is considered that there is an optimum value for the water concentration in the system.

[0055] The optimum value of the water concentration in the system is considered to vary depending on the reaction conditions. Factors that affect the reaction conditions include the type of alkane, the type of metal salt, the concentration of the metal salt, the type of p-benzoquinone, the concentration of p-benzoquinone, the amount of light irradiation, the oxygen concentration, the concentration of nitrite ions, etc. Therefore, it is advisable to determine the optimum value of the water concentration in the system in advance through preliminary experiments.

[0056] (Nitrite ion concentration) In the above catalytic reaction, it is considered that nitrite ions in the system contribute to the oxidation reaction of the reduced form DDQH2 of DDQ and regenerate DDQ. Therefore, as the amount of nitrite ions in the system increases, the regeneration cycle B of DDQ becomes easier to rotate. On the other hand, if the nitrite ions in the system increase too much, the nitrite ions are likely to cause a side reaction of reducing DDQ before photoexcitation (in the figure, symbol (VI)), and the DDQ contributing to the oxidation cycle A of alkanes may decrease. Therefore, it is considered that there is an optimum value for the nitrite ion concentration in the system.

[0057] The optimum value of the nitrite ion concentration in the system is considered to vary depending on the reaction conditions. Factors that affect the reaction conditions include the type of alkane, the type of metal salt, the concentration of the metal salt, the type of p-benzoquinone, the concentration of p-benzoquinone, the amount of light irradiation, the oxygen concentration, the concentration of water, etc. Therefore, it is advisable to determine the optimum value of the nitrite ion concentration in the system in advance through preliminary experiments.

[0058] (Metal salt concentration) In the above catalytic reaction, the metal salt-aqua complex in the system is oxidized, and the resulting chemical species oxidize the alkane. Therefore, when the amount of the metal salt-aqua complex increases, the oxidation cycle A of the alkane becomes easier to rotate. On the other hand, if the metal salt-aqua complex in the system increases too much, since there is too much metal salt relative to DDQ, it is considered that the number of metal ion species that stop the reaction at "LM (n+1)+ -OH" in the oxidation cycle A of the alkane increases. As a result, the oxidation cycle A of the alkane becomes difficult to rotate, and it is considered that the reaction is deactivated. Therefore, it is considered that there is an optimum value for the concentration of the metal salt-aqua complex in the system.

[0059] It is considered that the optimum value of the concentration of the metal salt-aqua complex in the system varies depending on the reaction conditions. Factors that affect the reaction conditions include the type of alkane, the type of para-benzoquinone, the concentration of para-benzoquinone, the amount of light irradiation, the oxygen concentration, the water concentration, the nitrite ion concentration, etc. Therefore, it is advisable to determine the optimum value of the concentration of the metal salt in the system in advance through preliminary experiments.

[0060] (Para-benzoquinone concentration) In the above catalytic reaction, the chemical species in the triplet excited state generated by the excitation of para-benzoquinone in the system rotate the oxidation cycle A of the alkane by oxidizing the metal salt-aqua complex. Therefore, when the amount of para-benzoquinone increases, the oxidation cycle A of the alkane becomes easier to rotate. On the other hand, since para-benzoquinone in the system is not a compound that directly oxidizes the alkane, there is a saturation amount of the amount contributing to the reaction. Therefore, it is considered that there is an optimum value for the concentration of para-benzoquinone in the system.

[0061] It is considered that the optimum value of the concentration of para-benzoquinone in the system varies depending on the reaction conditions. Factors that affect the reaction conditions include the type of alkane, the type of metal salt, the concentration of the metal salt, the amount of light irradiation, the oxygen concentration, the water concentration, the nitrite ion concentration, etc. Therefore, it is advisable to determine the optimum value of the concentration of the metal salt in the system in advance through preliminary experiments.

[0062] The concentration (molar concentration) of para - benzoquinone is preferably 0.5 times or more, more preferably 1 time or more, and even more preferably 1.5 times or more with respect to the concentration (molar concentration) of the metal salt. Also, the concentration (molar concentration) of para - benzoquinone is preferably 10 times or less, more preferably 5 times or less, and even more preferably 3 times or less with respect to the concentration (molar concentration) of the metal salt. The upper limit value and the lower limit value of the concentration ratio can be arbitrarily combined.

[0063] Ideally, the concentration (molar concentration) of para - benzoquinone is preferably 2 times that of the metal salt.

[0064] Under the reaction conditions set as described above, the method for producing an alkane oxide of the present embodiment can be carried out by introducing an alkane into the reaction system and irradiating it with light.

[0065] It is preferable to use a reaction vessel that is permeable to the irradiated light. The reaction vessel may be entirely permeable to light or may be a vessel having a light - collecting window in part.

[0066] Also, the reaction vessel itself may have light - shielding properties, and a light source for irradiating light of the above - mentioned wavelength may be arranged inside the reaction vessel, and the internal space of the vessel may be configured to be capable of light irradiation.

[0067] The reaction vessel may be a high - pressure reaction vessel. When such a reaction vessel is used, it becomes possible to charge air or gaseous alkane at an atmospheric pressure or higher into the gas phase, and it becomes possible to promote the reaction.

[0068] According to the method for producing an alkane oxide having the above - described configuration, it is possible to provide a method for producing an alkane oxide using oxygen as an oxidizing agent in a temperature environment lower than that of the prior art.

[0069] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. The various shapes, combinations, etc. of the constituent members shown in the above examples are merely examples, and can be variously changed based on design, specifications, etc. without departing from the gist of the present invention.

Example

[0070] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0071] In this example, the oxidation product was identified and quantified by measuring 1H-NMR using a nuclear magnetic resonance apparatus (Bruker, AVANCE III, 400 MHz). 1 1H-NMR was measured for identification and quantification.

[0072] (Experimental Example 1) Type of metal salt [Experimental Example 1-1] Under the atmosphere, a metal salt (0.2 mmol / L), DDQ (1.0 mmol / L), sodium nitrite (1.0 mmol / L), and H2O (1 mol / L) were dissolved in CD3CN, and the resulting reaction solution was charged into a light-transmissive pressure-resistant reaction vessel. Cu(OAc)2·H2O was used as the metal salt.

[0073] Furthermore, gaseous propane was charged into the pressure gauge attached to the reaction vessel until the pressure reached 0.7 MPa (gauge pressure). The gas phase in the reaction vessel was air.

[0074] While stirring the reaction solution, light (output 70%) emitted from a white LED light source (manufactured by Hayashi Repic Co., Ltd., Lumina Ace LA-HDF8010) was irradiated onto the reaction solution through an ultraviolet filter that cuts wavelengths of 390 nm or less. The output of the light before passing through the filter was 24.43 W, and the output of the light after passing through the filter was 22.42 W. Light irradiation was continued for 1 hour at room temperature (25°C) to carry out the oxidation reaction of alkane (propane).

[0075] After light irradiation, the 11H-NMR was measured to identify and quantify the oxidation products contained in the reaction. The quantification was determined by the internal standard method using benzonitrile as the internal standard.

[0076] Also, the turnover number (TON) of the catalyst was determined by the following formula. Turnover number (TON) = moles of alkane oxide / moles of metal salt

[0077] [Experimental Example 1-2] to [Experimental Example 1-7] The oxidation reaction of the alkane was carried out in the same manner as in Experimental Example 1-1, except that the metal salt used was changed as described in Table 1 below.

[0078] The types of oxidation products and the results of TON are shown in Table 1. Experimental Examples 1-1 to 1-7 are examples.

[0079] In Table 1, (1) to (6) indicate the types of products. The oxidation products are as follows. (1) 2-Propanol (2) Acetone (3) 2-Propyl hydroperoxide (4) 1-Propanol (5) Propanal (propionic acid) (6) 1-Propyl hydroperoxide

[0080]

Table 1

[0081] As a result of the evaluation, the oxidation reaction of the alkane proceeded by irradiating with light at room temperature for all metal salts. Among them, Experimental Example 1-1 using copper acetate was found to have a high turnover number and high reaction efficiency.

[0082] (Experimental Example 2) Concentration of metal salt [Experimental Example 2-1] to [Experimental Example 2-12] Using copper acetate as the metal salt, an alkane oxidation reaction was carried out in the same manner as in Experimental Example 1-1, except that the concentration of the metal salt was changed as shown in Table 2 below.

[0083] The types of oxidation products and the results of TON are shown in Table 2. Also, Figure 2 is a scatter plot showing the results of Experimental Example 2, with the metal salt concentration on the horizontal axis (unit: mmol / L) and the concentration of total alkane oxides on the vertical axis (unit: mmol / L).

[0084] Experimental Examples 2-2 to 2-12 are examples. Experimental Example 2-1 without using a metal salt is a comparative example.

[0085] In Table 2, the types of products indicated by (1) to (6) are the same as in Table 1. The numerical values shown in parentheses in the table indicate the concentration of each product (unit: mmol / L).

[0086]

Table 2

[0087] As a result of the evaluation, the production amount (concentration) of alkane oxides was maximum in Experimental Example 2-5, and the production amount (concentration) of alkane oxides decreased whether the concentration of copper acetate was decreased or increased. It was found that there is an optimum value for the concentration of the metal salt.

[0088] The above-mentioned experiments can be carried out as preliminary experiments for determining the concentration of the metal salt.

[0089] (Experimental Example 3) Concentration of p-benzoquinone [Experimental Example 3-1] to [Experimental Example 3-9] Using 0.5 mmol / L of copper nitrate and using DDQ as p-benzoquinone, an alkane oxidation reaction was carried out in the same manner as in Experimental Example 1-1, except that the concentration of DDQ was changed as shown in Table 3 below.

[0090] Table 3 shows the types of oxidation products and the results of TON. Figure 3 is a scatter plot showing the results of Experimental Example 3, with the DDQ concentration on the horizontal axis (unit: mmol / L) and the concentration of total alkane oxides on the vertical axis (unit: mmol / L).

[0091] Experimental Examples 3-2 to 3-9 are examples. Experimental Example 3-1 without using DDQ is a comparative example.

[0092] In Table 3, the types of products indicated by (1) to (6) are the same as those in Table 1. The numerical values shown in parentheses in the table indicate the concentration of each product (unit: mmol / L).

[0093]

Table 3

[0094] As a result of the evaluation, when the DDQ concentration was increased from Experimental Example 3-1 to 3-5, the production amount (concentration) of alkane oxides tended to increase. After Experimental Example 3-6, even when the DDQ concentration was increased, there was no significant change in the production amount (concentration) of alkane oxides. It was found that there is an optimum value for the DDQ concentration.

[0095] The above experiments can be carried out as preliminary experiments to determine the DDQ concentration.

[0096] (Experimental Example 4) Concentration of Nitrite [Experimental Example 4-1] to [Experimental Example 4-8] The alkane oxidation reaction was carried out in the same manner as in Experimental Example 1-1, except that the concentration of copper nitrate was 0.5 mmol / L and sodium nitrite was used as the nitrite, and the concentration of sodium nitrite was changed. All of Experimental Examples 4-1 to 4-8 are examples.

[0097] Figure 4 is a scatter plot showing the results of Experimental Example 4, with the sodium nitrite concentration on the horizontal axis (unit: mmol / L) and the concentration of total alkane oxides on the vertical axis (unit: mmol / L).

[0098] As a result of the evaluation, the production amount (concentration) of alkane oxides was maximized at a sodium nitrite concentration of 2.0 mmol / L, and the production amount (concentration) of alkane oxides decreased whether the concentration of sodium nitrite was decreased or increased. It was found that there is an optimum value for the concentration of sodium nitrite.

[0099] The above experiment can be carried out as a preliminary experiment for determining the concentration of sodium nitrite.

[0100] (Experimental Example 5) Concentration of water An oxidation reaction of alkane was carried out in the same manner as in Experimental Example 1-1 except that the concentration of copper nitrate was 0.5 mmol / L and the concentration of water was changed. All of Experimental Examples 5-1 to 5-7 are examples.

[0101] Figure 5 is a scatter diagram showing the results of Experimental Example 5, with the concentration of water on the horizontal axis (unit: mmol / L) and the concentration of total alkane oxides on the vertical axis (unit: mmol / L).

[0102] As a result of the evaluation, the production amount (concentration) of alkane oxides was maximized at a water concentration of 0.5 mol / L, and the production amount (concentration) of alkane oxides decreased whether the water concentration was decreased or increased. It was found that there is an optimum value for the water concentration.

[0103] The above experiment can be carried out as a preliminary experiment for determining the concentration of water.

[0104] (Experimental Example 6) Light intensity An oxidation reaction of alkane was carried out in the same manner as in Experimental Example 1-1 except that the concentration of copper nitrate was 0.5 mmol / L and the light intensity was changed.

[0105] Figure 6 is a scatter diagram showing the results of Experimental Example 6, with the intensity of the irradiated light on the horizontal axis (unit: %) and the concentration of total alkane oxides on the vertical axis (unit: mmol / L).

[0106] As a result of the evaluation, it was found that the light intensity and the total amount of oxidation products were linearly correlated, and that increasing the light intensity increased the amount of oxidation products.

[0107] (Experimental Example 7) Alkane Concentration An alkane oxidation reaction was carried out in the same manner as in Experimental Example 1-1, except that the concentration of copper nitrate was 0.5 mmol / L and the gauge pressure of propane injected into the reaction vessel was changed.

[0108] Figure 7 is a scatter diagram showing the results of Experimental Example 7, with the propane pressure on the horizontal axis (unit: MPa) and the concentration of total alkane oxides on the vertical axis (unit: mmol / L).

[0109] As a result of the evaluation, it was found that the propane pressure and the total amount of oxidation products were linearly correlated, and that increasing the propane pressure increased the amount of oxidation products. Since increasing the propane pressure in the reaction vessel also increased the amount (concentration) of propane dissolved in the reaction solution, it was found that increasing the alkane concentration in the reaction system increased the amount of oxidation products.

[0110] (Experimental Example 8) Reaction Time An alkane oxidation reaction was carried out in the same manner as in Experimental Example 1-1, except that the concentration of copper nitrate was 0.5 mmol / L and the reaction time (light irradiation time) was changed.

[0111] Figure 8 is a scatter diagram showing the results of Experimental Example 8, with the reaction time on the horizontal axis (unit: hours) and the concentration of total alkane oxides on the vertical axis (unit: mmol / L).

[0112] As a result of the evaluation, it was found that increasing the reaction time increased the amount of oxidation products.

[0113] (Experimental Example 9) Reactions of Methane and Ethane [Experimental Example 9-1] Under the atmosphere, Cu(OAc)2·H2O (0.5 mmol / L), DDQ (1.0 mmol / L), sodium nitrite (2.0 mmol / L), and H2O (0.5 mol / L) were dissolved in CD3CN, and the resulting reaction vessel was charged into a light-transmissive pressure-resistant reaction vessel.

[0114] Furthermore, gaseous ethane was charged into the pressure gauge attached to the reaction vessel until the pressure reached 0.95 MPa (gauge pressure). The gas phase in the reaction vessel was air.

[0115] While stirring the reaction solution, light (output 70%) emitted from a white LED light source (manufactured by Hayashi Repic Co., Ltd., Lumina Ace LA-HDF8010) was irradiated onto the reaction solution through an ultraviolet filter that cuts wavelengths of 390 nm and below. The output of the light before passing through the filter was 24.43 W, and the output of the light after passing through the filter was 22.42 W. Light irradiation was continued for 15 hours at room temperature (25 °C) to carry out the oxidation reaction of alkane (ethane).

[0116] After light irradiation, the 1 1H-NMR of the reaction solution was measured to identify and quantify the oxidation products contained in the reaction. Quantification was determined by the internal standard method using benzonitrile as the internal standard.

[0117] [Experimental Example 9-2] An oxidation reaction of alkane was carried out in the same manner as in Experimental Example 9-1, except that the concentration of Cu(OAc)2·H2O was 0.05 mmol / L.

[0118] [Experimental Example 9-3] An oxidation reaction of alkane was carried out in the same manner as in Experimental Example 9-1, except that methane was used as the alkane.

[0119] [Experimental Example 9-4] An oxidation reaction of alkane was carried out in the same manner as in Experimental Example 9-2, except that methane was used as the alkane.

[0120] Table 4 and 5 show the types of oxidation products and the TON results. The numerical values shown in parentheses in the table indicate the concentration of each product (unit: mmol / L).

[0121]

Table 4

[0122]

Table 5

[0123] As a result of the evaluation, it was confirmed that when the method for producing an alkane oxide of the present invention was used, even gaseous alkanes having a high C-H bond dissociation energy such as methane and ethane could be oxidized to obtain oxidation products.

[0124] Based on the results of Experimental Example 4, even if alkanes having a C-H bond dissociation energy smaller than that of methane, such as gaseous butane or liquid hexane, are used as reaction substrates, it is considered that alkane oxides can be obtained by the method for producing an alkane oxide of the present invention.

[0125] From the above, it was found that the present invention is useful.

Claims

1. A step of irradiating a reaction solution containing an alkane, para - benzoquinone having an electron - withdrawing group, a metal salt, and water with light in an oxygen - containing atmosphere, The reaction temperature in the above step is 0 °C or higher and lower than the boiling point of the solvent of the reaction solution, The metal element contained in the metal salt is at least one selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu, The wavelength band of the light includes the maximum absorption wavelength of the para - benzoquinone, The method for producing an alkane oxide, wherein the para - benzoquinone is 2,3 - dichloro - 5,6 - dicyano - p - benzoquinone or tetrachloro - 1,4 - benzoquinone.

2. The method for producing an alkane oxide according to Claim 1, wherein the reaction solution further contains nitrite ions.

3. The method for producing an alkane oxide according to Claim 1 or 2, wherein the metal element is Cu.

4. The method for producing an alkane oxide according to Claim 3, wherein the metal salt is copper acetate.

5. The method for producing an alkane oxide according to any one of Claims 1 to 4, wherein the solvent of the reaction solution is acetonitrile.

6. The method for producing an alkane oxide according to any one of Claims 1 to 5, wherein the reaction temperature is 10 °C or higher and 40 °C or lower.

7. The method for producing an alkane oxide according to any one of Claims 1 to 6, wherein the alkane contains at least one selected from the group consisting of methane, ethane, propane, and butane.

Images