JPH0580459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing 2,6-dihydroxynaphthalene, and more particularly to a method for producing highly pure 2,6-dihydroxynaphthalene.

(Prior Art) 2,6-dihydroxynaphthalene can be obtained by oxidizing 2,6-diisopropylnaphthalene to produce 2,6-diisopropylnaphthalene dihydroperoxide, and acid decomposing this with an acidic catalyst. This 2,6-dihydroxynaphthalene is industrially useful, for example, as a raw material for synthetic resins, synthetic fibers, pharmaceuticals, agricultural chemicals, dyes, and the like.

U.S. Pat. No. 4,503,262 discloses that 2,6-diisopropylnaphthalene is dissolved in an organic solvent and oxidized with molecular oxygen in the presence of a heavy metal salt catalyst, such as organic acid cobalt, to produce 2,6-diisopropylnaphthalene. In the method for producing naphthalene dihydroperoxide, in particular, the organic solvent has 5 carbon atoms.
It is stated that the reaction rate, yield and purity of the desired dihydroperoxide can be improved by using ~14 aliphatic hydrocarbon solvents, such as n-heptane.

However, conventionally, 2,6-
2,6-
There is no known industrial method for obtaining dihydroxynaphthalene, but only by oxidizing β-isopropylnaphthalene, which is a related compound of 2,6-diisopropylnaphthalene, with molecular oxygen in the presence of an aqueous base solution. A method for producing β-isopropylnaphthalene hydroperoxide was published in 1983.
It is only described in Publication No. 34138 and British Patent No. 654035. In addition, Japanese Patent Publication No. 55-31764 discloses that diisopropylbenzenes are oxidized to diisopropylbenzene dihydroperoxide,
A method for producing hydroquinone or resorcinol by decomposing it in the presence of an acidic catalyst is described.

As described above, there are several prior art techniques regarding the oxidation of 2,6-diisopropylnaphthalene and the acid decomposition reaction after the oxidation reaction of its related compounds, but the acid decomposition reaction of 2,6-diisopropylnaphthalene dihydroperoxide Conventionally,
There is almost no prior technology. In particular, 2,6-diisopropylnaphthalene is oxidized with molecular oxygen in the presence of an aqueous base solution to produce 2,6-diisopropylnaphthalene dihydroperoxide, which is then decomposed with an acidic catalyst to produce 2,6-diisopropylnaphthalene. - In the reaction to obtain dihydroxynaphthalene, 6-isopropyl-2-naphthol derived from the acid decomposition of 2,6-diisopropylnaphthalene monohydroperoxide, which is an intermediate to dihydroperoxide in the oxidation reaction, is produced as a main by-product. However, until now, nothing has been known about a method for separating this by-product from the acid decomposition reaction mixture to obtain highly pure 2,6-dihydroxynaphthalene.

(Object of the Invention) The present inventors have prepared 2,6-dihydroxynaphthalene by oxidation of 2,6-diisopropylnaphthalene with molecular oxygen in the presence of an aqueous base solution and subsequent acid decomposition reaction using an acidic catalyst. As a result of intensive research on the production method, we found that in the process of isolating 2,6-dihydroxynaphthalene from the reaction mixture after acid decomposition reaction, by adding aromatic hydrocarbons to this mixture at any stage,
The 6-isopropyl-2-naphthol and other by-products coexisting with 2,6-dihydroxynaphthalene can be effectively removed, and the resulting solution of 2,6-dihydroxynaphthalene crude crystals can be treated with activated carbon. The inventors have discovered that 2,6-dihydroxynaphthalene of extremely high purity can be easily obtained by the above method, leading to the present invention.

Therefore, the present invention provides a method for producing highly pure 2,6-dihydroxynaphthalene by subjecting an oxidation reaction mixture obtained by oxidizing 2,6-diisopropylnaphthalene to an acid decomposition reaction, and then subjecting it to a purification treatment. The purpose is to provide.

(Structure of the Invention) The method for producing 2,6-dihydroxynaphthalene according to the present invention is a method for producing 2,6-dihydroxynaphthalene obtained by oxidizing 2,6-diisopropylnaphthalene with molecular oxygen.
- When producing 2,6-dihydroxynaphthalene by acid decomposing diisopropyl naphthalene dihydroperoxide in the presence of an acidic catalyst, after the above acid decomposition reaction, (a) adding an aromatic hydrocarbon to the acid decomposition reaction mixture, a step of extracting and removing by-products coexisting with 2,6-dihydroxynaphthalene, and (b) contacting a solution containing crude 2,6-dihydroxynaphthalene with activated carbon, and then extracting purified 2,6-dihydroxynaphthalene from this solution. It is characterized by performing a step of isolating.

The oxidation reaction of 2,6-diisopropylnaphthalene is carried out by adding 2,6-diisopropylnaphthalene to an aqueous base solution and mechanically mixing to form an emulsified state.
This is done by blowing a gas containing molecular oxygen into this.

As the base, an alkali metal compound is preferably used. Specific examples of the alkali metal compound include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and the like. The concentration of these alkali metal compounds in the aqueous solution is preferably 20% by weight or less. Also, the amount of base aqueous solution used in the reaction mixture is
Generally, it is preferred that it accounts for 5 to 80% by weight of the reaction mixture, particularly preferably in the range of 20 to 70% by weight. The amount of base aqueous solution used is 5% of the reaction mixture.
When it is less than % by weight, oily unreacted 2,6
- The reaction liquid consisting of diisopropylnaphthalene and its oxidation product and an aqueous base solution is not well dispersed, resulting in insufficient emulsification, which adversely affects the oxidation reaction. On the other hand, the amount of base aqueous solution used is
If the amount exceeds 80% by weight, the emulsification state of the reaction system deteriorates, which is not preferable. Further, in the oxidation reaction, the pH of the aqueous base solution is usually maintained in the range of 7 to 12.

Note that 2,6-diisopropylnaphthalene and its oxidation product and an aqueous base solution can usually be sufficiently emulsified by mechanical stirring.
If necessary, the mixture may be stirred in the presence of a conventionally known emulsifier such as stearic acid.

As the base, alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide, and strontium hydroxide can also be used. especially,
Calcium hydroxide is preferred. These alkaline earth metal hydroxides may be used alone, or
It may be used in combination with the alkali metal compound.

As molecular oxygen, oxygen gas may be used alone, but air is usually sufficient. The required amount of molecular oxygen is usually determined by the preparation for the oxidation reaction2,
The amount is in the range of 5 to 15 Nl/hour in terms of oxygen gas per 100 g of 6-diisopropylnaphthalene, but is not particularly limited.

The reaction temperature is usually 80 to 150°C, preferably 90°C.
~130°C, and the reaction time varies depending on conditions such as reaction temperature, but is usually 6 to 40 hours.
The reaction rate of 2,6-diisopropylnaphthalene is
80 to increase the amount of dihydroperoxide produced.
% or more is preferable. Incidentally, the reaction is usually carried out under normal pressure, but it can also be carried out under increased pressure or reduced pressure, if necessary.

In the above oxidation reaction of 2,6-diisopropylnaphthalene, a reaction initiator is preferably used. For example, α,α'-azobis(cyclohexane-1-carbonitrile) can be used as a reaction initiator. By using a reaction initiator, the induction period of the reaction can be shortened.
The amount used is usually in the range of 0.005 to 1 part by weight per 100 parts by weight of the charged reaction mixture containing the raw material 2,6-diisopropylnaphthalene.

By the oxidation reaction of 2,6-diisopropylnaphthalene as explained above, 2,6-diisopropylnaphthalene dihydroperoxide (hereinafter referred to as
It's called DHP. ), as a by-product, 2-
(2-hydroxy-2-propyl)-6-(2-hydroperoxy-2-propyl)naphthalene (hereinafter referred to as HHP), 2,6-bis(2-hydroxy-2-propyl)naphthalene (hereinafter referred to as DCA)
That's what it means. ), 2-isopropyl-6-(2-hydroxy-2-propyl)naphthalene (hereinafter referred to as MCA
That's what it means. ), and 2-isopropyl-6-(2-hydroperoxy-2-propyl)naphthalene (hereinafter referred to as MHP) is produced.
That's what it means. ) is formed.

To determine the composition of the reaction product from the above oxidation reaction, separate the organic phase and aqueous phase after the reaction, extract the aqueous phase with ether, etc., and analyze the organic phase and ether extract using liquid chromatography. if,
Unreacted 2,6-diisopropylnaphthalene and oxidation reaction products DHP, HHP, DCA, MHP,
MCA etc. can be quantified.

In the present invention, in the oxidation reaction of 2,6-diisopropylnaphthalene, as described above,
The reaction rate is preferably 80% or more, and the oxidation reaction mixture containing unreacted 2,6-diisopropylnaphthalene, the dihydroperoxide, and by-products is subjected to the next acid decomposition reaction. In the method of the present invention, usually an appropriate amount of an appropriate organic solvent such as methyl isobutyl ketone (MIBK) is added to the oxidation reaction mixture, the organic phase containing the oxidation reaction mixture is separated from the aqueous phase, and the organic phase is separated from the aqueous phase. Perform the following acid decomposition using Hereinafter, this organic phase may be referred to as an acid-decomposed raw material.

In the present invention, 2,6-dihydroxynaphthalene is produced by using the above acid-decomposed raw material and acid-decomposing the 2,6-diisopropylnaphthalene dihydroperoxide contained therein in the presence of an acidic catalyst. In this case, the acid-decomposed raw material contains
Since the carbinols mentioned above are included as by-products of the oxidation reaction, by coexisting hydrogen peroxide at the same time as the acid decomposition reaction, HHP and DCA of the by-product carbinols are converted to dihydroperoxides. It is preferable to oxidize the dihydroperoxide and simultaneously decompose the dihydroperoxide with an acidic catalyst, if necessary, because 2,6-dihydroxynaphthalene can be obtained in a high yield.

In the present invention, when the reaction rate of 2,6-diisopropylnaphthalene is 80% or more,
In addition to DHP, the yield of HHP and DCA also increases, but
HHP and DCA can be converted to DHP if hydrogen peroxide is allowed to coexist at the same time during the acid decomposition reaction, making it possible to obtain 2,6-dihydroxynaphthalene in high yield. Moreover, in this case, the yield of MHP that does not contribute to the production of 2,6-dihydroxynaphthalene can be reduced, which is preferable. In particular, by controlling the reaction rate of 2,6-diisopropylnaphthalene to 90% or more, more preferably 95% or more, 2,6-
The yield of dihydroxynaphthalene can be further increased.

As the above-mentioned hydrogen peroxide, in addition to hydrogen peroxide or an aqueous hydrogen peroxide solution, substances that generate hydrogen peroxide under reaction conditions, such as sodium peroxide and calcium peroxide, can be used. Preferably, an aqueous hydrogen solution is used. In particular, in the method of the present invention, 0.9 to 2 mol, preferably 1.0 to 2 mol, preferably 1.0 to 2 mol, of hydrogen peroxide is added per mol of alcoholic hydroxyl group of the carbinols during the acid decomposition reaction.
By using it in a proportion of 1.5 mol, the desired 2,6-dihydroxynaphthalene can be obtained in high yield. Further, when hydrogen peroxide is used under such conditions, it is possible to significantly suppress the production of by-products due to the condensation of carbinols at the same time, which is preferable.

In addition, as acidic catalysts in acid decomposition reactions,
Inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, strong acidic ion exchange resins, solid acids such as silica gel and silica alumina, organic acids such as chloroacetic acid, methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, phosphotungstic acid, phosphorus Heteropolyacids such as molybdic acid are preferably used. These acidic catalysts may be added to the reaction system as they are, or if these acidic catalysts have solubility, they may be dissolved in an appropriate inert solvent and added to the reaction system. The amount of acidic catalyst used depends on its type and reaction conditions, but it is usually 0.5 to 0.5 to
It is in the range of 10% by weight.

In the present invention, as mentioned above, 2,6-
After the oxidation reaction of diisopropylnaphthalene, it is practically advantageous to transfer 2,6-diisopropylnaphthalene dihydroperoxide and by-products from the reaction mixture into an organic solvent such as MIBK, and perform the acid decomposition reaction using this organic solvent as a reaction solvent. It is.
However, the reaction solvent is not limited to MIBK at all, and other inert organic solvents may be used as necessary, such as ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol, acetic acid, propionic acid, etc. Hydrocarbons such as lower aliphatic carboxylic acids, benzene, toluene, xylene, hexane, heptane, etc. can also be used,
Moreover, mixtures of these can also be used.

This acid decomposition reaction is carried out at 0 to 100°C, preferably at 20°C.
It is carried out at a temperature of ~80°C.

In the method of the present invention, aromatic hydrocarbons are added to the acid decomposition reaction mixture obtained as described above, and by-products coexisting with 2,6-dihydroxynaphthalene are extracted and removed; High purity 2,6-dihydroxynaphthalene is obtained by bringing a solution containing -dihydroxynaphthalene into contact with activated carbon and then isolating 2,6-dihydroxynaphthalene from this solution.

In the method of the present invention, the aromatic hydrocarbon may be added to the acid decomposition reaction mixture at any stage of isolating the reaction product, 2,6-dihydroxynaphthalene, according to an appropriate method, but for example, This can be done by the following method.

First, after the acid decomposition reaction is completed, the acidic catalyst contained in the resulting reaction mixture is neutralized with an alkaline aqueous solution, and then the organic solvent is distilled off to separate two liquid phases: an aqueous phase and an oil phase. After that, the oil phase is separated from the two liquid phases of oil and water, and the organic solvent is further distilled off from the oil phase, and aromatic hydrocarbons are added to the concentrate. According to this method, reaction by-products are extracted into aromatic hydrocarbons, while 2,6-dihydroxynaphthalene is precipitated from aromatic hydrocarbons as crystals.

Second, water was added to the concentrate obtained as described above to form a slurry containing 2,6-dihydroxynaphthalene as a solid content, aromatic hydrocarbons were added to this, and the solid content was dissolved by heating. After that, the oil phase is extracted and the aqueous phase is cooled to precipitate 2,6-dihydroxynaphthalene. On the other hand, reaction by-products are extracted and removed to aromatic hydrocarbons.

Thus, by concentrating the acid decomposition reaction mixture and mixing it with aromatic hydrocarbons in the presence or absence of water, the reaction by-products are extracted and removed to the aromatic hydrocarbons; 6- which is the main by-product
2,6-dihydroxynaphthalene from which most of the isopropyl-2-naphthol has been removed can be obtained as crude crystals. Aromatic hydrocarbons for this purpose include, for example, benzene, toluene,
Xylene, trimethylbenzenes, cumene, cymene, diisopropylbenzene and the like are preferably used.

Then, according to the method of the present invention, the above 2,6-
Diisopropylnaphthalene crude crystals are dissolved under heating in a solvent suitable for recrystallization and purification, such as water or a mixed solvent of water and acetone, to form a solution, which is treated with activated carbon and then cooled. By recrystallizing, even trace amounts of colored substances can be removed and almost pure 2,6-dihydroxynaphthalene can be obtained. Examples of the recrystallization solvent include water, lower alcohols such as methanol, ethanol, and propyl alcohol, aliphatic ketones such as acetone, methyl ethyl ketone, and MIBK, and chain or cyclic ethers such as diethyl ether, dioxane, and tetrahydrofuran. Further examples include acetonitrile, nitromethane, etc., which may be used alone or in combination.

Furthermore, the method of treating the 2,6-dihydroxynaphthalene crude crystal solution with activated carbon and the type of activated carbon used are not particularly limited, but for example, treatment using a packed column method using granular activated carbon is one of the preferred methods. be.

(Effect of the invention) As described above, according to the method of the present invention, 2,6
- When producing 2,6-dihydroxynaphthalene by acid decomposition of the reaction mixture obtained by the oxidation reaction of diisopropylnaphthalene, 6-isopropyl-2- is the main by-product of the acid decomposition reaction.
Extremely pure 2,6-dihydroxynaphthalene, which does not contain naphthol or any coloring substances, can be obtained.

(Examples) The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 75 g of 2,6-diisopropylnaphthalene, 75 g of a 4.5% aqueous sodium hydroxide solution, and α,α′-bis( Cyclohexane-1-carbonitrile) 0.1g was charged, reaction temperature was 100℃, pressure was 5.
While the contents were vigorously stirred at Kg/cm ² G, air was blown in at a rate of 20 kg/cm 2 G to carry out the reaction for 9 hours. The reaction rate of 2,6-diisopropylnaphthalene was 99.5%.

After adding 150 g of methyl isobutyl ketone to the obtained oxidation reaction product, the oil phase (methyl isobutyl ketone phase) and the water phase were separated. As a result of liquid chromatography analysis, the composition of the oxidation products contained in this oil phase is as follows: DHP 6.5% by weight HHP 13.4% by weight DCA 6.3% by weight MHP 2.7% by weight MCA 1.6% by weight Other (assuming the molecular weight is 212) It was 7.6% by weight.

Next, 28.3 g of acetone solution containing 1.7% by weight sulfuric acid was charged into a 1-capacity glass reaction vessel equipped with a rotary stirrer, a reflux condenser, an acid decomposition raw material supply pipe, and an acidic catalyst solution supply pipe, and the mixture was placed in a hot water bath at a temperature of 65°C. This reaction vessel was placed on top. When the acetone began to reflux due to heating, a mixture of 236 g of the MIBK solution (oil phase) of the oxidation product, 17.2 g of 60% hydrogen peroxide solution, and 73 g of acetone was started to be supplied from the acid decomposition raw material supply pipe. At the same time as this acid decomposition raw material starts being supplied, an acetone solution containing 1.7% sulfuric acid is introduced from the acidic catalyst solution supply pipe.
Feeding of 43g was also started and stopped after 1 hour. Note that the feed amounts of the decomposition raw material and the acetone solution of sulfuric acid were determined using a small metering pump. After this, 3 more
A time reaction was performed.

The acid decomposition reaction described above was carried out twice, and the resulting reaction mixtures were combined. As a result of liquid chromatography analysis, the composition of the acid decomposition reaction product was as follows: 2,6-dihydroxynaphthalene 9.6% by weight 6-isopropyl-2-naphthol 2.0% by weight 2,6-diisopropylnaphthalene 0.1% by weight Others (molecular weight: 6%) (same as -isopropyl-2-naphthol) was 4.0% by weight.

Next, 150g of the above acid decomposition reaction mixture
was taken, and in order to neutralize the sulfuric acid contained therein, a 2% aqueous sodium carbonate solution was gradually added until the pH of the solution reached approximately 4. Thereafter, in order to remove acetone and MIBK contained in the acid decomposition reaction mixture, the following concentration operation was performed. That is, first,
Acetone was distilled off under normal pressure using a rotary evaporator to obtain two liquid phases, an aqueous phase and an oil phase, and the oil phase and the aqueous phase were separated. MIBK was distilled off from the separated oil phase again under reduced pressure of 20 to 30 mmHg using a rotary evaporator to obtain a concentrate. However, MIBK
The distillation of was stopped just before crystal precipitation started.

This concentrate contained 21.6% by weight of 2,6-dihydroxynaphthalene and 4.4% by weight of 6-isopropyl-2-naphthol.

290 g of cumene was charged into a 500 ml separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a concentrate dropping port, and placed on a water bath at a temperature of 70°C.
69 g of the concentrate was gradually dropped into this flask to precipitate crystals. After the dropwise addition was completed, the temperature of the hot water bath was gradually lowered to further precipitate crystals, and finally the solution was cooled to room temperature to sufficiently precipitate crystals.

Thereafter, the crystals were filtered and dried to obtain 23 g of 2,6-dihydroxynaphthalene crude crystals (2,6
-dihydroxynaphthalene crystallization recovery rate 80%). The crude crystals thus obtained contained 50.7% by weight of 2,6-dihydroxynaphthalene and 0.7% by weight of 6-isopropyl-2-naphthol.

The dried crude crystals were added to 100 g of acetone/water (20/80) mixed solvent and dissolved by heating. After adding 1 g of activated carbon powder to this solution and stirring thoroughly,
The activated carbon was filtered off, and the resulting filtrate was transferred to a 300 ml volumetric flask equipped with a stirrer and allowed to cool while stirring to precipitate 2,6-dihydroxynaphthalene crystals. After cooling to room temperature and sufficiently precipitating crystals, the crystals were filtered off and dried under reduced pressure. The purity of this 2,6-dihydroxynaphthalene crystal is
As a result of gas chromatography analysis, it was 99.9%, and the melting point was 220.5-222.5°C.

Example 2 100g of acid decomposition reaction mixture obtained in Example 1
After neutralizing the sulfuric acid with a 2% aqueous sodium carbonate solution in the same manner as in Example 1, the acetone was distilled off to obtain two liquid phases, an aqueous phase and an oil phase, and the oil phase and the aqueous phase were separated. separated.

The separated oil phase was placed in a 300 ml separable flask equipped with a stirrer, a thermometer, a distillate extractor, and a dropping funnel, and placed on an oil bath at a temperature of 100-110°C to azeotropically distill MIBK with water. It was distilled off as a mixture. The water lost from the reaction mixture as the azeotrope was distilled off was replenished from the dropping funnel in a timely manner. After MIBK was distilled off, the reaction mixture became a slurry.

Next, water was added to this slurry containing 2,6-dihydroxynaphthalene to make 130 g, and the slurry was transferred to a 300 ml glass autoclave.
After charging 50 g and pressurizing with nitrogen to 5 Kg/cm ² G, the contents were heated to 160° C. and stirred. After the solid content was completely dissolved, heating and stirring were stopped, and the contents were allowed to stand still. After extracting the oil phase from the contents, stirring of the contents was started again and the contents were allowed to cool. When the contents reached approximately room temperature, the contents were removed and filtered to obtain 11.5 g of wet crude crystals of 2,6-dihydroxynaphthalene. 6 in this crude crystal
-The proportion of isopropyl-2-naphthol is 2,
It was 1.2% based on 6-dihydroxynaphthalene.

11 g of the above crude crystals were dissolved in 135 g of a 20% acetone aqueous solution, and treated with activated carbon and recrystallized in the same manner as in Example 1 to obtain 8.1 g of purified 2,6-dihydroxynaphthalene crystals. Purity 99.8%, melting point
The temperature was 220.9-222.0°C.

Claims (1)

[Claims] 1. 2,6-dihydroxynaphthalene is obtained by acid decomposition of 2,6-diisopropylnaphthalene dihydroperoxide obtained by oxidizing 2,6-diisopropylnaphthalene with molecular oxygen in the presence of an acidic catalyst. In producing 2,6-dihydroxynaphthalene, after the acid decomposition reaction, (a) adding aromatic hydrocarbons to the acid decomposition reaction mixture and extracting and removing by-products coexisting with 2,6-dihydroxynaphthalene; and (b) crude 1. A method for producing 2,6-dihydroxynaphthalene, which comprises bringing a solution containing 2,6-dihydroxynaphthalene into contact with activated carbon, and then isolating purified 2,6-dihydroxynaphthalene from the solution.