JPH10182525A - Hydroxylation of benzene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce phenol by incorporating in the phenol production process steps of hydroxylating benzene by irradiating UV light to a liquid mixture which contains benzene, dipenylsulfoxide and acetic acid, and also oxidizing diphenyl sulfide produced as a by-product to diphenyl sulfoxide. SOLUTION: This production of phenol comprises charging a liquid mixture of benzene, dephenyl sulfoxide and acetic acid into a reaction vessel equipped with a cooling tube and a quartz tube for UV light irradiation inside the vessel, irradiating UV light to the mixture to produce phenol by hydroxylation of benzene, photooxidizing the formed diphenyl sulfide in the presence of a photosensitizer, such as Methylene Blue, to regenerate diphenyl sulfoxide, and recycling the solution of regenerated diphenyl sulfoxide, thus efficiently producing phenol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing phenol from benzene, and more particularly to a method for hydroxylating benzene. More specifically, a phenol is produced by irradiating a mixture containing benzene, diphenylsulfoxide and acetic acid with ultraviolet rays. A method for hydroxylating benzene.

[0002]

2. Description of the Related Art Many direct hydroxylations of benzene by a catalytic reaction have been reported.

[0003] For example, JP-A-7-232984 produces phenol from benzene using oxygen gas as an oxidizing agent at 25 ° C in the presence of sulfuric acid and a CuCl catalyst.

Japanese Patent Application Laid-Open No. Hei 7-238042 discloses that a reaction is carried out at 130 ° C. in the presence of CO—O ₂ gas using a catalyst in which Pd or Rh and V are supported on a carrier such as silica. Manufactures phenol from benzene.

Further, JP-A-6-192150 discloses that P
The oxidation reaction is performed by using oxygen gas in the presence of h ₃ P and H ₂ O or an acid catalyst.

[0006] Each of the above reactions may be carried out under strong acidity, or may be carried out under high temperature.
Due to severe reaction conditions, there are cases where there is a practical problem, and there are also cases where it cannot be applied to aromatic compounds having a functional group.

On the other hand, a method using a photoreaction has also been proposed. According to this method, the reaction conditions are mild. For example, J. Am. Chem. SOC. , 1995, 11
7, 2667. Discloses that irradiation with ultraviolet light in the presence of benzene and dibenzothiophene sulfoxide produces phenol. However, in this method, since the solubility of the dibenzothiophene sulfoxide used in the reaction solvent is small, the amount that can be treated by one reaction is small. For this reason, mass production is difficult.

Further, the reaction of reoxidizing dibenzothiophene produced by the above-mentioned photoreaction to dibenzothiophene sulfoxide is possible only under special reaction conditions using hydrogen peroxide, and various oxidation methods using molecular oxygen are possible. Either do not react or all become sulfonic acid. For this reason, it is difficult to reoxidize dibenzothiophene to dibenzothiophene sulfoxide, and it is difficult to reuse this for the above-mentioned photoreaction. Therefore, the above-mentioned photoreaction has a problem of poor practicality in production.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies to develop an excellent method for direct hydroxylation of benzene which can solve the above-mentioned problems. As a result, diphenylsulfoxide was converted to dibenzothiophene. It has a higher solubility than sulfoxide, and it can be dissolved in a large amount in acetic acid solvent. In addition, sulfide generated by photoreaction using diphenyl sulfoxide is photooxidized by oxygen gas using a sensitizer (singlet oxygen oxidation). It is easily oxidized to the original diphenyl sulfoxide,
This has been found to be reusable for the hydroxylation reaction, and that the presence of oxygen in the reaction system improves the selectivity of phenol production in the above-mentioned hydroxylation reaction, thereby completing the present invention.

Therefore, it is an object of the present invention to produce phenol by directly hydroxylating benzene under mild conditions, and to regenerate a sulfide formed as a result of the reaction into a sulfoxide to recycle the benzene. Another object of the present invention is to provide an optimization method.

[0011]

According to the present invention, there is provided a hydroxylation of benzene, comprising irradiating a mixture containing at least benzene, diphenylsulfoxide and acetic acid with ultraviolet rays. It proposes a method.

The present invention also relates to a method for irradiating a mixture containing at least benzene, diphenylsulfoxide and acetic acid with ultraviolet rays to hydroxylate benzene, and then converting the diphenylsulfide produced by the hydroxylation into a sensitizer. The present invention proposes a method for hydroxylating benzene, characterized in that diphenylsulfoxide is reused by an oxidation reaction of reacting with oxygen by irradiating with light in the presence.

The present invention further provides at least benzene,
After irradiating ultraviolet rays to a mixture containing diphenylsulfoxide and acetic acid to hydroxylate benzene, the following steps (A), (B), and (A) diphenylsulfide formed by the hydroxylation is used as a sensitizer. A process for producing a regenerating solution for regenerating diphenyl sulfoxide by an oxidation reaction of reacting with oxygen by irradiating light with light in the presence of the compound; The present invention proposes a method for hydroxylating benzene, which comprises repeating the conversion step a predetermined number of times.

Hereinafter, the present invention will be described in detail.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The method for hydroxylating benzene of the present invention is represented by the following reaction formula (I).

[0016]

Embedded image As shown in (1), a phenol (4) is produced by irradiating a mixture containing at least benzene (1), diphenylsulfoxide (2) and acetic acid (3) with ultraviolet rays to produce phenol (4). is there. In this reaction, diphenyl sulfoxide is converted to diphenyl sulfide (5), and biphenyl (6) is by-produced.

The mixing ratio of acetic acid and benzene is acetic acid 1
The amount of benzene is preferably from 1 to 50 g, particularly preferably from 1.5 to 30 g, per 00 ml. When the mixing ratio of benzene is less than 1 g, the reaction efficiency tends to deteriorate, and when it exceeds 50 g, the ratio of the ultraviolet rays absorbed by benzene and contributing to the reaction decreases, so that the reaction hardly proceeds.

The mixing ratio of acetic acid to diphenyl sulfoxide (2) is preferably 1 to 50 g of diphenyl sulfoxide per 100 ml of acetic acid, and 2 to 20 g.
g is particularly preferred. When the mixing ratio of diphenylsulfoxide is less than 1 g, the efficiency of the benzene oxidation reaction tends to be low, and when it exceeds 50 g, the diphenylsulfoxide may partially remain without being dissolved in acetic acid.

The ultraviolet rays to be irradiated may be those having any wavelength in the wavelength range of 150 to 400 nm, and those having a single wavelength peak or those having a plurality of wavelength peaks in the above wavelength range may be used. And may further include visible light. There is no particular limitation on the irradiation amount of the ultraviolet ray, but the reaction time can be shortened as the irradiation amount increases. Therefore, it is preferable to increase the irradiation amount within a practically feasible range. A commercially available ultraviolet irradiation device can be appropriately used.

The reaction temperature may be any room temperature, and specifically, preferably 10 to 40 ° C. If the reaction temperature is lower than 10 ° C., acetic acid may coagulate, and in this case, the reaction rate tends to decrease. When the reaction temperature exceeds 40 ° C., decomposition of diphenylsulfoxide becomes remarkable, which may be disadvantageous from the viewpoint of production cost.

The reaction proceeds even in the absence of oxygen. However, when oxygen is present, the by-product of biphenyl (6) is suppressed, and the selectivity of phenol is improved. As a method for supplying oxygen to the mixed solution, a method of bubbling an oxygen gas or a gas containing oxygen into the mixed solution, a method of performing a reaction under an oxygen atmosphere in a closed system (including a pressurized state), and the like. Can be illustrated. In view of the oxygen gas dissolution efficiency and the simplicity of the apparatus, a method of bubbling is generally preferred. The higher the oxygen concentration in the mixture, the faster the reaction proceeds. Therefore, it is preferable that the oxygen concentration be close to the saturation concentration.

Examples of the gas containing oxygen include a mixed gas of an inert gas such as a nitrogen gas and an oxygen gas, and air.

The reaction time is not particularly limited, but is usually preferably 30 minutes or more. If the reaction time is short, the yield of phenol is small, and even if the reaction is performed indefinitely for a long period of time, the yield of phenol does not increase in proportion to the reaction time. However, when diphenyl sulfoxide described below is recycled, it is naturally not limited to this.

In the present invention, the diphenyl sulfide formed in the hydroxylation of benzene can be reoxidized to diphenyl sulfoxide, which can be recycled.

That is, diphenyl sulfoxide is consumed in the oxidation reaction of benzene to form diphenyl sulfide, which can be easily reoxidized by the following method or the like. (1) Using hydrogen peroxide as an oxidizing agent and using W, M as a catalyst
A method using an oxide such as o, Mn, Ti, V, a halide, or an organometallic complex thereof. (2) Co, Mn, C as a catalyst using molecular oxygen as an oxidizing agent
A method using an oxide such as u or Cr, a halide, or an organometallic complex thereof. (3) A photooxidation (singlet oxygen oxidation) method using a sensitizer in the presence of oxygen.

Considering the selectivity of phenol, the photo-oxidation method (3), in which the reaction proceeds under particularly mild conditions, is preferred.

Examples of the sensitizer used in the photooxidation method (3) include rose bengal, methylene blue, tetraphenylporphyrin (TPP), thionin, erythrosine, eosin Y, fluorescein, proflavine, fluorenone, benzophenone, coronene and the like. it can. Of these, methylene blue and rose bengal are preferred,
Particularly, methylene blue is desirable.

As a reaction solvent used in the photooxidation method (3), a saturated aliphatic carboxylic acid having 1 to 6 carbon atoms or a lower alcohol such as methanol or ethanol can be used, but from the viewpoint of solubility and the like, Acetic acid is particularly preferred.

Examples of the oxygen used in the photooxidation method (3) include oxygen gas, a mixed gas of oxygen gas and an inert gas such as nitrogen, and air. Examples of the method for supplying oxygen include a method in which oxygen gas or a gas containing oxygen is blown into the mixed solution by bubbling, a method in which a reaction is performed in an oxygen atmosphere in a closed system (including a pressurized state), and the like. In view of the oxygen gas dissolution efficiency and the simplicity of the apparatus, a method of bubbling is generally preferred.

As the light or light source used for the light irradiation (3), sunlight, a fluorescent lamp, a tungsten-halogen lamp,
Any type of high-pressure mercury lamp or the like can be used, but a fluorescent lamp, a tungsten-halogen lamp, and a high-pressure mercury lamp with high visible light energy efficiency are particularly preferable.

In the present invention, diphenyl sulfide may be reoxidized to diphenyl sulphoxide as described above and recovered, but as shown in the following reaction formula (II), the recirculation step (A) , (B) can also be incorporated into the hydroxylation process.

[0032]

Embedded image As described above, the reaction solution obtained by irradiating ultraviolet rays to a mixture containing at least benzene, diphenyl sulfoxide, and acetic acid to produce phenol from benzene contains unreacted benzene, diphenyl sulfide, and the like. doing. Step (A) is a step of irradiating visible light using a sensitizer while supplying oxygen to the reaction solution to reoxidize diphenyl sulfide (5) to diphenyl sulfoxide (2) to produce a regenerating solution. is there.

The step (B) is a step of irradiating the regenerating solution obtained in the step (A) with ultraviolet rays and reacting diphenyl sulfoxide obtained by reoxidation in the step (A) with unreacted benzene. . Then, if necessary, the above steps (A),
By repeating (B) a desired number of times, unreacted benzene is successively converted into phenol to increase the overall yield.

According to the hydroxylation method incorporating the above-mentioned recycle step, the diphenyl sulfide is oxidized to diphenyl sulfoxide in the reaction solution without isolation, and is subsequently reacted with unreacted benzene. Thus, this reaction can be a continuous reaction without an isolation step in all the steps, so that the reaction is efficient.

When diphenyl sulfide is present in a certain amount or more with respect to diphenyl sulphoxide, it is photolyzed to produce a by-product. Specifically, when the concentration of diphenyl sulfoxide is lower than 6.7 g / l, the decomposition of diphenyl sulfide generated by the oxidation reaction of benzene becomes severe. Therefore, in order to recycle diphenyl sulfide, it is preferable to maintain the concentration of diphenyl sulfide in a concentration range of 6.7 g / or more where decomposition of diphenyl sulfide is small.

As a result, a large amount of diphenylsulfoxide is used when a recycling step is incorporated, but from an industrial point of view, by recycling and using diphenylsulfoxide, the entire reaction system can be used. It is advantageous to use a circulating method capable of suppressing the decomposition without increasing the proportion of diphenyl sulfide.

The phenol produced by the above reaction is
It can be separated and recovered from the raw material benzene and acetic acid. Examples of the separation method include a method of distilling off benzene and the like by an ordinary method.

Hereinafter, the present invention will be described specifically with reference to examples. The present invention is not limited to these examples.

[0039]

【Example】

Example 1 10 g of diphenylsulfoxide and 6 parts of benzene were placed in a reaction vessel equipped with a cooling tube and an inner tube for ultraviolet irradiation made of quartz.
g and acetic acid in a ratio of 300 ml were added.
A 200 W high-pressure mercury lamp (manufactured by Ishii Rika Kikai, Ltd.) was attached to the inner tube, and ultraviolet irradiation was started. The mixture was stirred while the temperature of the mixture was kept at 20 ° C., and the photoreaction was continued for 3 hours. Then, the stirring and the irradiation of ultraviolet rays were stopped. A part of the obtained reaction solution was injected into a gas chromatograph (GC-14A, manufactured by Shimadzu Corporation), and the amount of phenol produced was measured. The amount of phenol produced was 86.4 mg, and the amount of biphenyl was 44.7 mg. Phenol selectivity over phenol and biphenyl (phenol production /
(Phenol production + Biphenyl production) x 10
0) was 65.9% by weight.

Example 2 A phenol was produced in the same manner as in Example 1 except that 10 g of diphenylsulfoxide, 60 g of benzene and 250 ml of acetic acid were used. The amount of phenol produced is 91.2m
g and biphenyl were 208.2 mg. The selectivity of phenol over phenol and biphenyl was 30.5.
wt%.

Example 3 Phenol was produced in the same manner as in Example 1 except that a ball filter was further attached to the reaction vessel, and oxygen was bubbled through the mixture at a flow rate of 100 ml / min. The amount of phenol produced is 139.2 mg, and the amount of biphenyl is 1
0.3 mg. The selectivity of phenol over phenol and biphenyl was 93.1 wt%.

Example 4 Phenol was produced in the same manner as in Example 3 except that the reaction time was changed to 6 hours. The amount of phenol produced is 20
9.3 mg and biphenyl were 16.4 mg. The selectivity of phenol over phenol and biphenyl is 9
2.7 wt%.

Example 5 Example 3 was repeated except that a mixture of 10 g of diphenylsulfoxide, 60 g of benzene and 250 ml of acetic acid was used.
Phenol was produced in the same manner as described above. The amount of phenol produced was 1026.0 mg, and the amount of biphenyl was 135.1 mg.
Met. The selectivity of phenol over phenol and biphenyl was 88.4 wt%.

Example 6 Example 3 was repeated except that a mixture of 50 g of diphenylsulfoxide, 30 g of benzene and 270 ml of acetic acid was used.
Phenol was produced in the same manner as described above. The amount of phenol produced was 371.1 mg and the amount of biphenyl was 40.2 mg. The selectivity of phenol to phenol and biphenyl was 90.2 wt%.

Example 7 Phenol was produced in the same manner as in Example 3 except that the gas to be bubbled was air instead of oxygen gas.
The amount of phenol produced is 124 mg, and the amount of biphenyl is 36 m.
g. The selectivity of phenol to phenol and biphenyl was 77.5 wt%.

Example 8 The reaction solution after the reaction of Example 5 was added to a 300 ml reaction vessel equipped with an inner tube for light irradiation, a ball filter for oxygen bubbling, a cooling tube, and a thermometer. Further, 0.016 g of methylene blue was added. Oxygen gas was blown into the reaction solution through a ball filter at a flow rate of 100 ml / min, followed by stirring. Visible light irradiation was started with a 400 W halogen lamp, and the reaction was cooled in an ice bath to maintain the reaction temperature at 20 ° C., and oxidation of diphenyl sulfide was performed for 3 hours.

After completion of the reaction, a part of the obtained reaction solution was injected into a gas chromatograph and analyzed. 98.0 wt% or more of diphenyl sulfide (diphenyl sulfide formed under the conditions of Example 5) before this reaction was converted to diphenyl sulfide. The selectivity was 99.0 wt% or more.

Using the reaction solution thus obtained, benzene was hydroxylated again for 3 hours by the method of Example 5. The yield of phenol was 2018.7 mg and the yield of biphenyl was 271.5 mg.

Comparative Example 1 Phenol was produced under the same conditions as in Example 3. However,
Diphenyl sulfoxide was not added. When the amount of phenol produced was measured in the same manner as in Example 1, 43.0 mg of phenol was produced. Biphenyl was not detected.

[0050]

According to the method for hydroxylating benzene of the present invention, a mixture of diphenylsulfoxide, benzene and acetic acid is irradiated with ultraviolet light, so that the direct hydroxylation of benzene can be easily performed under mild conditions. Can be performed. In this case, the starting material diphenylsulfoxide is convenient because it can be easily produced and is a readily available compound. Furthermore, acetic acid dissolves diphenylsulfoxide at a high concentration, so that the present hydroxylation method requires a large throughput. When oxygen is present, the selectivity of the reaction is further increased, and the phenol of the target compound can be produced efficiently.

Further, it is easy to reoxidize diphenyl sulfide generated by the hydroxylation reaction to diphenyl sulfoxide. By incorporating this step into the hydroxylation method, phenol can be produced more efficiently.

Further, since this reaction does not require the addition of various catalysts and various additives which are difficult to remove from the reaction system, the separation and recovery of phenol after the completion of the reaction becomes extremely simple. Therefore, the method for producing the present phenol has characteristics such as being a very industrially advantageous method.

Claims (5)

[Claims] 1. A method for hydroxylating benzene, comprising irradiating a mixture containing at least benzene, diphenylsulfoxide and acetic acid with ultraviolet rays. 2. The method for hydroxylating benzene according to claim 1, wherein oxygen is present in the mixture. 3. A method comprising irradiating a mixture containing at least benzene, diphenylsulfoxide, and acetic acid with ultraviolet rays to hydroxylate benzene, followed by the following steps (A), (B), and (A): A regenerating solution producing step of regenerating diphenyl sulfoxide by oxidizing diphenyl sulfide generated by the above, and (B) a hydroxylating step of hydroxylating benzene by irradiating the regenerating solution obtained in the step (A) with ultraviolet rays. A method for hydroxylating benzene, which is repeated a number of times. 4. The method for hydroxylating benzene according to claim 3, wherein oxygen is present in the mixed solution and the regenerating solution. 5. The hydroxylation method of benzene according to claim 3, wherein the oxidation in the step (A) is a photo-oxidation reaction of irradiating with light to react with oxygen in the presence of a sensitizer.