JP2866715B2 - Method for producing aromatic hydroxy compound - Google Patents

Description

The present invention relates to a method for producing an aromatic hydroxy compound, and more particularly to a method for producing a hydroxy compound by hydroxylating phenols and / or alkoxybenzenes with hydrogen peroxide. Regarding improvement.

Hydroxy compounds obtained by the method of the present invention are, for example, para-methoxy-phenol, hydroquinone, and catechol, and are useful as various organic synthetic intermediates or raw materials, reducing agents, rubber drugs, dyes, It is used in the fields of medicines, fragrances, polymerization inhibitors, oxidation inhibitors, rubber medicines and the like.

[Conventional technology]

The method of hydroxylating phenols using hydrogen peroxide has long been known as divalent iron ion (Fenton's reagent)
Reaction in the presence of a strong acid, such as sulfuric acid, etc. [Nature, 165 , 401 (195
0)] or a method using hydrofluoric acid [J. Org, Chem., 35 ,
4028 (1970)], a method using a cobalt salt [Chem. Abs]
t., 80 133015g, 81 , 151787k] and the like.

These methods are disadvantageous in that since the catalyst is a homogeneous system, it is complicated to separate the catalyst from the reaction product and obtain the desired product, or there is a problem in the post-treatment of a highly corrosive acid. was there.

Subsequently, a method was proposed in which a heterogeneous catalyst, which can easily separate the catalyst from the reaction system, and a crystalline substance containing silicon oxide and titanium oxide were used [GB2,083,816, 2,116,97].
Four]. In this method, since the catalyst is a heterogeneous system, it is only necessary to mechanically separate the catalyst from the product after the reaction, which is an industrially advantageous method. However, the method of using crystalline silicon oxide and titanium oxide-based compounds as catalysts has drawbacks in that the activity of the catalyst used is insufficient and that the catalyst activity varies depending on the catalyst preparation method.

[Problems to be solved by the invention]

Conventionally, hydroxylation of phenols with hydrogen peroxide catalyzed by crystalline silicon oxide and titanium oxide-based compounds is, as described above, inadequate activity of the catalyst or in each production batch of catalyst activity. There are problems such as the fluctuation of

An object of the present invention is to provide a method for producing an aromatic hydroxy compound, which has no problems as in the conventional method and has high efficiency.

[Means for solving the problem]

In order to solve these problems, the present inventors have conducted various studies on a method for producing an aromatic dihydroxy compound or an alkoxyphenol using phenols and hydrogen peroxide, and particularly on a catalyst used for a hydroxylation reaction. Regarding the hydroxylation reaction with some kinds of hydrogen peroxide, the use of a crystalline material containing silicon oxide and titanium oxide of specific crystallite size, which has not been reported before, as a catalyst, enables the desired product to be efficiently produced. Have been obtained, and the present invention has been completed.

That is, the present invention provides a method for producing aromatic hydroxy compounds by hydroxylating phenols and / or alkoxybenzenes with hydrogen peroxide in the presence of a crystalline substance containing silicon oxide and titanium oxide. A method for producing an aromatic hydroxy compound, characterized in that a crystalline substance containing titanium having a crystallite size of less than 10,000 ° is used.

According to the present invention, aromatic dihydroxy compounds or alkoxyphenols are produced.

The definition of the crystallite size of the catalyst used in the method of the present invention is a value obtained by the method described below. That is, a method of observing the size of a secondary electron image of an ordinary scanning electron microscope and directly measuring the crystallite size is used.

Usually, the crystallite size of the crystal is calculated from the half width of the powder X-ray diffraction. However, the crystalline compound of the method of the present invention has a crystallite size of about 5000 ° or less and a relatively large crystallite size. Therefore, in the ordinary powder X-ray diffraction, a grinding treatment in which the sample is ground in a mortar or the like is necessary for the purpose of pretreatment of the sample.

If the crystallite size is about 1000 ° or less, the crystallite size hardly changes by grinding, but in the method of the present invention, in some cases, in the grinding process using a mortar, etc., there is a risk that the crystallite size changes. Instead of using the half width method of powder X-ray diffraction, a method of measuring the size of crystallites using a scanning electron microscope is employed. Specific examples of the scanning electron micrograph showing the size of the crystallite size are shown in Examples and Comparative Examples.

A crystalline substance containing silicon oxide and titanium oxide having a crystallite size of less than 10,000 mm is prepared, for example, by the following method.

Alcohol solution or aqueous solution such as titanium salt, titanium tetrachloride, titanic acid, titanium alkoxide such as titanium sulfide or titanium isopropoxide, water source glass, colloidal silica sol or silicon ethyl etc. An alcohol solution or an aqueous solution and a quaternary ammonium salt aqueous solution are mixed while appropriately adjusting the pH to obtain a gel-like precipitate. When this precipitate is hydrothermally synthesized under heating at 100 to 250 ° C., a crystalline compound is obtained.

The ratio of silica / titanium of the crystalline substance used in the method of the present invention is usually Si / Ti = 20 to 200 (atomic ratio) in many cases.

In addition, a catalyst composed of crystalline silicon and titanium oxides can be used irrespective of the production method and starting materials, as long as the crystallite size falls within the range of the method of the present invention.

In the method of the present invention, alkoxybenzenes or phenols are reacted with or without a solvent in the presence of a crystalline compound having the above-mentioned crystallite size.

When a solvent is used, alcohols such as methanol or tertiary butyl alcohol are frequently used, and the reaction is carried out by adding 5 to 50% by weight of alkoxybenzenes and phenols as substrates to the solvent. As alkoxybenzenes, anisole, ethoxyphenol, and the like are used. As phenols, phenol, ortho-
Alkyl phenols such as cresol and meta-cresol are used.

The amount of the crystalline compound composed of titania and silica, which is a catalyst, is suitably in the range of 0.1 to 30% by weight based on the substrate in the case of a batch reaction.

As the hydrogen peroxide used, an aqueous solution of hydrogen peroxide can be used, and there is no need to use anhydrous hydrogen peroxide, and there is no danger of explosion, which is one of the features of the present invention. Usually 30
An aqueous solution of 6060 wt% hydrogen peroxide is used.

The amount of hydrogen peroxide to be used is 0.3 times to equimolar to phenols as a substrate. That is, the reaction conditions are set so as to keep the concentration of residual hydrogen peroxide in the reaction-terminated liquid sufficiently low.

The reaction temperature is often in the range of 40 to 100 ° C, particularly 50 to 90 ° C. The time required for the reaction is, for example, in the case of a batch reaction, in the range of 1 to 10 hours.

〔Example〕

 Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

(Example 1) In a 200 ml flask, 34.2 g of tetraethoxysilicon (164 mmol) and 1.9 ml of tetraisopropoxytitanium (6.4 mmol) were added and mixed under a nitrogen atmosphere. To this, 38.9 g of a 25% aqueous solution of tetrapropylammonium hydroxide was gradually added dropwise with stirring. By stirring at 90 ° C. for 3 hours, 30 ml of ethanol was distilled off. Transfer the residue to an autoclave with a titanium lining and add another 800 ml
Of deionized water was added. Under self-generated pressure at 175 ° C,
Heated for 7 hours with gentle stirring.

After cooling the autoclave, take out the contents, centrifuge, extract the supernatant, wash with water, repeat centrifugation several times,
The precipitate was washed and dried at 110 ° C. for 4 hours. Then, the temperature was gradually raised to 500 ° C. under air flow, and the mixture was calcined at 500 ° C. for 5 hours. The powder X-ray diffraction pattern of the product was in good agreement with the diffraction pattern of crystalline titanosilicate. From the scanning electron micrograph, the crystallite size was 3000 ° (first
Figure).

0.4 g of the powdery crystalline titanosilicate obtained by the above method, 15 g of tertiary butyl alcohol and 1.5 g of phenol were added to a 30 ml flask equipped with a cooling tube, and heated to 85 ° C. with stirring. To this, 1.5 g of a 30% aqueous hydrogen peroxide solution was added dropwise over 30 minutes. Thereafter, stirring was continued at 90 ° C. for another 2 hours to carry out a hydroxylation reaction.

After completion of the reaction, the flask was centrifuged, and the supernatant was recovered and analyzed by gas chromatography. The yield of hydroquine was 28% based on hydrogen peroxide, the yield of catechol was 26%, and the total yield of dihydroxy compounds was 54% based on hydrogen peroxide.

(Comparative Example _{-1) Ti 2 (SO 4)} 3 · 8H 2 O 1.07g, NaCl 3.60g, tetrapropylammonium bromide 1.72 g, was added and mixed H ₂ SO ₄ 1.82 g of deionized water 17.4 g (A liquid). JIS No. 3 22.1 g of water glass and 14.5 g of deionized water were mixed (Solution B). Na
Cl 12.2g, tetrapropylammonium bromide 0.7
g, NaOH 0.72 g and H ₂ SO ₄ 0.60 g were mixed with deionized water 62.0 g (Solution C).

The solution A and the solution B were simultaneously injected into the solution C by means of a trace amount pump. During this time, the solution C is sufficiently stirred and the pH of the solution C
Was maintained in the range of 10 to 10.5, and the injection rates of both the solutions A and B were adjusted. The time required for the injection was 20-30 minutes. Although a gel-like precipitate was formed by the injection, stirring was continued for another 30 minutes for aging. Next, the mother liquor containing the precipitated gel was treated with a homogenizer to homogenize, and then charged into an autoclave for hydrothermal synthesis. The autoclave used had a structure in which the contents were not in contact with metal using a lining made of alkali-resistant glass.

The autoclave was heated while stirring at a rate of 2 to 3 revolutions / second, and the temperature was raised to 150 ° C over 2 hours, and then raised to 210 ° C over 3 hours. Stirring was further continued at 210 ° C. for 3 hours, and then the apparatus was allowed to cool. The content of the obtained autoclave is washed with deionized water, dried, and then dried under air circulation for 550 minutes.
C. and baked for 4 hours. Then, after an ion exchange treatment with an aqueous solution of (NH ₄ ) ₂ CO ₃ , the mixture was calcined at 450 ° C. for 3 hours and used as a catalyst.

The X-ray diffraction pattern of the obtained catalyst was in good agreement with that of crystalline titanosilicate. Observation with a scanning electron microscope showed that the average crystallite size was 30,000 ° (FIG. 2).

Using this catalyst, the same reaction as in Example 1 was performed.
The yield of the obtained hydroquinone is 0.7 based on hydrogen peroxide.
%, The yield of catechol was 0.6%, and the yield of dihydroxybenzene was 1.3%.

(Examples 2 to 4 and Comparative Examples 2 to 3) Hydroxyl of anisole was obtained in the same manner and under the same reaction conditions as in Example 1 using a compound composed of crystalline silica and titania having different crystallite sizes as a catalyst. Was implemented. The crystals obtained are shown in the following table.

[Effects of the Invention] According to the method of the present invention, hydroxylation of phenols and alkoxybenzenes with hydrogen peroxide can be efficiently advanced at a high reaction rate, and industrially advantageous dihydroxyphenols and alkoxylated Phenols can be obtained.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph showing the crystal structure of the catalyst used in Example 1. FIG. 2 is a scanning electron micrograph showing the crystal structure of the catalyst used in Comparative Example 1.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C07B 61/00 300 C07B 61/00 300

Claims (1)

(57) [Claims] 1. A method for producing an aromatic hydroxy compound by hydroxylating phenols and / or alkoxybenzenes with hydrogen peroxide in the presence of a crystalline substance containing silicon oxide and titanium oxide. A method for producing an aromatic hydroxy compound, characterized by using a crystalline substance containing a crystallite having a crystallite size of less than 10,000 °.