JPH0529340B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a novel 1,
This invention relates to a method for producing 4,4a,9a-tetrahydroanthraquinone (hereinafter abbreviated as THAQ). More specifically, the production of THAQ is characterized by the Diers-Alder reaction of 1,4-naphthoquinone obtained by liquid phase oxidation of naphthalene using an acidic aqueous solution containing ceric ions and 1,3-butadiene. It is the law. THAQ is industrially useful as an intermediate for anthraquinone dyes.

[Prior Art] The method of manufacturing THAQ is well known. For example, JP-A No. 51-8256, JP-A No. 51-8257, JP-A No. 57-48936.
Each publication describes a method for producing THAQ by removing by-product acidic components from 1,4-naphthoquinone obtained by gas-phase oxidation of naphthalene, and then subjecting it to a Diels-Alder reaction with 1,3-butadiene. It has been stated.

In addition, as a method for producing 1,4-naphthoquinone,
A method for producing 1,4-naphthoquinone by oxidizing naphthalene using an acidic aqueous solution containing ceric ions is also well known. For example, naphthalene dissolved in an organic solvent that is immiscible with water is oxidized using an acidic aqueous solution containing ceric ions,
Method for producing 1,4-naphthoquinone
-34978 Publication), a method for producing 1,4-naphthoquinone characterized by suspending powdered naphthalene in an aqueous solution of ceric salt using a dispersant (Japanese Unexamined Patent Publication No. 56-61321) etc. The acidic aqueous solution containing ceric ions used in these oxidation reactions is ceric ammonium nitrate.
Nitric acid aqueous solution, ceric nitrate-nitric acid aqueous solution, cerium nitrate-nitric acid aqueous solution, etc. are generally used. Further, the process of the liquid phase oxidation reaction includes an electrochemical regeneration process as a method of regenerating cerium ions produced after the liquid phase oxidation reaction into cerium ions.

[Problems to be solved by the invention] However, 1,4-naphthoquinone obtained by gas phase oxidation of naphthalene is used as a raw material.
In the THAQ manufacturing method, organic acids such as phthalic anhydride, maleic anhydride, or benzoic acid are produced as by-products through gas phase oxidation of naphthalene, and 1,4-naphthoquinone is separated and purified from the oxidation reaction product by an extraction method or the like. However, it is not easy to remove the by-product acids, and the resulting crude 1,4-naphthoquinone also contains these by-product acids. The THAQ product obtained by subjecting 1,4-naphthoquinone containing such impurities and 1,3-butadiene to the Diels-Alder reaction also has the problem of low yield and low quality.

On the other hand, in a method for producing 1,4-naphthoquinone in which naphthalene is oxidized in a liquid phase using an acidic aqueous solution containing ceric ions, the higher the concentration of ceric ions in the acidic aqueous solution, the higher the oxidation reaction. The higher the temperature, the higher the reaction rate, which is advantageous in terms of the yield of the target oxide per unit time.However, from the standpoint of selectivity of the target oxide, the concentration of ceric ions in the acidic aqueous solution increases. The lower the concentration or the lower the oxidation reaction temperature, the more advantageous it is. Furthermore, on the high temperature side, problems such as coloring of the product and corrosion of the equipment also occur. Based on these considerations, the liquid phase oxidation reaction temperature is usually preferably 40 to 80°C, and the concentration of ceric ions is also set after appropriate consideration. However, the conventional methods have not been able to satisfy all aspects such as reaction rate, ie, productivity, yield, and purity of the obtained 1,4-naphthoquinone. In addition, when a ceric ammonium nitrate-nitric acid aqueous solution is used as the acidic aqueous solution containing ceric ions, the solubility of ceric ammonium nitrate is high, so the ceric ion concentration can be maintained at a high concentration, but the amount of by-products produced is Furthermore, when a cerium sulfate-sulfuric acid aqueous solution is used, the solubility of cerous sulfate produced in the oxidation reaction with ceric sulfate is low, and it is necessary to avoid precipitation of cerium salt during the reaction. This method has the disadvantage that the concentration of ceric ions in the cerium nitrate-sulfuric acid aqueous solution becomes low, resulting in a slow reaction rate.

The present invention eliminates the above-mentioned drawbacks and provides high-purity
The present invention provides a method for producing THAQ with high selectivity and high productivity.

[Means for Solving the Problem] As a result of intensive study on the shortcomings of the previous conventional method, the present inventors first oxidized naphthalene in a liquid phase using an acidic aqueous solution containing ceric ions under ultrasonic irradiation. 1,4-naphthoquinone with few by-products can be obtained with high selectivity by liquid-phase oxidation of The present invention was completed based on the discovery that the present invention can be obtained using the following methods. That is, the present invention comprises: (a) a step of liquid-phase oxidation of naphthalene under ultrasonic irradiation using an acidic aqueous solution containing ceric ions; 4-
A step of separating crystals containing naphthoquinone from an acidic aqueous solution containing cerium ions; , 4a, 9a - a step of crystallizing and separating crystals containing tetrahydroanthraquinone, (d) electrolytically oxidizing the acidic aqueous solution containing cerium ions separated in step (b) to remove
This method for producing THAQ is characterized by the following steps: oxidizing cerium ions to ceric ions and returning to step (a). This will be explained in more detail below.

The process (b) of liquid phase oxidation of naphthalene using an acidic aqueous solution containing ceric ions under ultrasonic irradiation has conventionally been carried out under forced stirring using a stirrer, external circulation, gas blowing, etc. However, in the present invention, ultrasonic irradiation is carried out, preferably in combination with forced stirring. Ultrasonic irradiation allows a much higher reaction rate than simple forced stirring alone, lowering the reaction temperature or shortening the reaction time, increasing productivity, and allowing the reaction to proceed with high selectivity. do. In addition, since there are few by-products, the next step (b) can be achieved with sufficient purity by using a relatively simple separation device.
Crystals containing naphthoquinone are obtained.

Ultrasonic waves only need to have a frequency of 10 KHz or higher, and the irradiation method can be either external irradiation method or internal irradiation method. Also, devices with individual frequencies and outputs can be used as ultrasound generators. The sound wave radiator may be of any type, such as a flat plate type, ring type, or disc type. Irradiation can be carried out continuously or intermittently during the reaction, and it is also effective to carry it out only in the latter stage of the reaction when the reaction rate decreases.

In the present invention, as described above, by ultrasonic irradiation, a much higher reaction rate can be obtained than by mere forced stirring, and the reaction temperature can be lowered or the reaction time can be shortened. Therefore, the preferred reaction temperature in step (a) of the present invention is usually 0 to 80°C,
More preferably 0-60℃, still more preferably 15-35
It is ℃. If the temperature is too low, the reaction rate decreases, and if the temperature is too high, it is disadvantageous in terms of hydrolysis of the ceric salt, contamination of side reaction products such as polymerization, coloring, or corrosion of the equipment.

Regarding the acid concentration of the acidic aqueous solution containing ceric ions in step (a), if it is too low, the ceric ions will become unstable, while if it is too high, the solubility of the ceric ions will decrease and the equipment will be corroded. Therefore, the acid concentration in the acidic aqueous solution is preferably 0.3 to 10 mol/, more preferably 0.7 to 2.
The range is mol/. As the acid, the above-mentioned No. 2
An acid corresponding to the anion forming the cerium ion source can be used, but other acids can also be added, for example, sulfuric acid, nitric acid, etc. can be used alone or in combination. The concentration of cerium ions in the acidic aqueous solution containing ceric ions may be such that cerium salts do not precipitate during the oxidation reaction.

As the acidic aqueous solution containing ceric ions, an acidic aqueous solution containing ceric ions produced by liquid-phase oxidation of naphthalene is recovered, and an acidic aqueous solution containing ceric ions regenerated by electrolytic oxidation is used. Furthermore, for new preparations or replenishments, acidic aqueous solutions of various ceric salts or acidic aqueous solutions of ceric salts obtained by oxidizing various ceric salts can be used.

In addition, in the step (a), naphthalene may be dissolved in an organic solvent that is immiscible with water, or naphthalene alone may be added without using a solvent.
The system may be in liquid or slurry form. Examples of the organic solvent include aromatic hydrocarbons such as benzene, tert-butylbenzene, and chlorobenzene, or substituted products thereof, cyclohexane, n-hexane, n-
Organic solvents such as aliphatic hydrocarbons such as pentane and n-octane, and chlorinated aliphatic hydrocarbons such as carbon tetrachloride, chlormethylene and dichloroethane can be used.

In step (b), 1,4-naphthoquinone crystals are crystallized from the reaction mixture obtained in step (a), separated into the crystals and liquid by centrifugation, filtration, etc., and further separated from the liquid if necessary. The acidic aqueous solution phase containing cerium ions and the organic phase are separated, and the crystals are sent to step (c), and the acidic aqueous solution containing cerium ions is sent to step (d). The organic phase mainly has a solubility of 1,4
- Naphthoquinone, unreacted naphthalene or (a)
It consists of the melt filters, etc. used in step (2), and is sent to step (d) without being separated from the aqueous phase, or separated,
It is collected and returned to step (a).

In step (c), 1,4-naphthoquinone is subjected to a Diers-Alder reaction with 1,3-butadiene. The reaction is carried out using a suitable solvent to dissolve the 1,4-naphthoquinone and 1,3-butadiene. Examples of such solvents include benzene, toluene,
Aromatic hydrocarbons such as xylene, cyclohexane, n
- Aliphatic hydrocarbons such as hexane, n-pentane, and n-octane; halogenated hydrocarbons such as dichloroethane, carbon tetrachloride, and dichlorobenzene; ethers such as ethyl ether and diphenyl ether;
Esters such as dioctyl phthalate and methyl acetate, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol,
Examples include cellosolves such as methyl cellosolve and ethyl cellosolve. The Diels-Alder reaction of 1,4-naphthoquinone and 1,3-butadiene is generally carried out at a temperature of 0 to 250°C, preferably 30 to 150°C, as in the case of other aromatic quinone compounds. If the reaction temperature is too high, the solubility of 1,3-butadiene will decrease and the reaction will be difficult to proceed.
In addition, the generated THAQ is converted into other substances through side reactions such as isomerization and dehydrogenation, and side reactions such as polymerization of raw materials 1,4-naphthoquinone and 1,3-butadiene also occur, reducing reaction selectivity. . On the other hand, if it is too low, the reaction rate will decrease. The reaction pressure depends on the solubility of 1,3-butadiene, etc., but is usually 120Kg/cm ²
Hereinafter, it is more generally carried out in the range of 0 to 20 kg/cm ² . The more excess 1,3-butadiene is used relative to 1,4-naphthoquinone, the faster the reaction will be completed, but if it is too much, it is not economical in terms of equipment, and it is preferably 1 to 20 times the molar amount. , more preferably 1.1 to 10 times the molar amount. Further, the reaction time is limited by constraints such as the concentration of 1,3-butadiene, reaction temperature, reaction pressure, etc., and the optimum reaction time is selected for each.

The electrolytic oxidation step (iv) is preferably performed using a diaphragm. If performed without using a diaphragm, for example, the first
When an acidic aqueous solution containing cerium ions contains nitrate ions, the nitrate ions may be reduced to nitrite ions or ammonium ions on the cathode side by electrolytic oxidation. In that case, the concentration of each ion changes, the pH of the liquid changes, and the ability of the ceric ion as an oxidizing agent changes accordingly, so settings such as reaction conditions must also be changed.
Further, ceric ions generated at the anode diffuse and are reduced to cerium ions again at the cathode, resulting in a decrease in current efficiency. For this reason, it is preferable to perform electrolytic oxidation by using a diaphragm in the electrolytic oxidation step, applying an acidic aqueous solution containing cerium ions to the anolyte, applying an electrolyte to the catholyte, and separating both solutions by the diaphragm. The diaphragm should preferably have the ability to prevent the above-mentioned disadvantages, and various ion exchange membranes are preferably used. Fluorine-based cation exchange membranes or anion exchange membranes are excellent in terms of durability and are more suitable.

Next, an embodiment based on the present invention will be explained in detail with reference to FIG. 1. Figure 1 is a flow sheet for continuously producing THAQ using a solvent in a liquid phase oxidation reaction. In Fig. 1, 1 is a catholyte tank, 2 is an electrolytic tank, 3-a and 3-b are anolyte tanks, 4 is a liquid phase oxidation reactor, 5 is an extraction column, 6 is a solvent tank, and 7 is a diesel tank. 8 is a 1,3-butadiene tank, 9 is a filter, 10 is a distillation column, 11 is a naphthalene tank, and 12 is a dryer.

The cathode and anode of the electrolytic cell 2 are separated by a diaphragm, and the catholyte in the catholyte tank 1 is passed through the line 13.
is introduced into the cathode side of the electrolytic cell 2 and circulated through the line 14 to the catholyte tank 1, while the anolyte tank 3
The acidic aqueous solution containing cerium ions in -a is introduced into the anode side of the electrolytic cell 2 through line 15 and sent through line 16 to the anolyte tank 3-b. During this time, electrolysis is performed to oxidize the cerium ions in the acidic aqueous solution to cerium ions. a second concentration of a predetermined concentration;
The anolyte containing cerium ions is in the anolyte tank 3-
Naphthalene is introduced from the naphthalene tank 11 into the liquid phase oxidation reactor 4 via line 26 from b through line 17, where naphthalene is subjected to catalytic liquid phase oxidation with ceric ions. The reaction product is introduced into the extraction column 5 via line 18, where the 1,4-naphthoquinone is extracted into the solvent phase by the solvent introduced from the solvent tank 6. The first after extraction,
The acidic aqueous solution phase containing cerium ions is returned to the anolyte tank 3-a through the line 20, regenerated into cerium ions in the electrolytic cell 2, and recycled. On the other hand, the solvent phase in which 1,4-naphthoquinone was dissolved was introduced into the Diels-Alder reactor 7 via line 19, and was heated to an appropriate temperature with 1,3-butadiene introduced from the 1,3-butadiene tank 8.
Diels-Alder reaction under pressure. Since the generated THAQ precipitates as crystals, the reaction mixture is separated in a filter vessel 9. The THAQ crystals are washed, sent to a dryer 12, and dried to become a product.
On the other hand, the liquid is sent to a distillation column 10 and separated into a solvent and unreacted naphthalene, which are recovered and reused in a solvent tank 6 and a naphthalene tank 11, respectively.

[Examples] Next, the present invention will be explained in detail by examples.
The present invention is not limited to this.

Example 1 Pt plated Ti electrode for anode, SUS316L electrode for cathode,
Fluorine-based cation exchange membrane (manufactured by DuPont,
Current density in electrolytic cell 2 equipped with Nafion 423)
Electrolyze 0.3 mol of ceric and ceric sulfate/1 mol of sulfuric acid/aqueous solution at 15A/ ^dm2 ,
An anolyte solution containing 0.15 mol of cerium/0.15 mol of ceric sulfate/1 mol of sulfuric acid/aqueous solution was obtained. The catholyte was a 1 mol/aqueous sulfuric acid solution. The current efficiency was 95%.

Nitric acid aqueous solution containing the obtained ceric ions
33,700Kg and 100Kg of naphthalene dissolved in n-hexane 610Kg were placed in a reactor, and the mixture was stirred at 25℃.
After internal irradiation with 28KHz, 400W ultrasonic waves and reaction for about 40 minutes, the reaction mixture was transferred to extraction tower 5, and 3900Kg of n-hexane was further added to remove undissolved 1,4-naphthoquinone in the aqueous phase. was extracted. Charge the n-hexane phase to Diers-Alder reactor 7, add 75.3 kg to the 1,3-butadiene tank, and
The reaction was carried out at 3 Kg/cm ² at ℃ for 2 hours. After cooling and washing the obtained crystals with n-hexane,
It was dried at 80°C for 4 hours to obtain 144.7 kg of THAQ crystals. When the obtained product was analyzed by gas chromatography and infrared spectroscopy, it was found that the purity was 99.0%.
It was confirmed that it was THAQ.

Comparative Example 1 Reaction, extraction, filtration, washing,
As a result of drying, the yield of THAQ crystals was 130.2Kg.
It was hot.

[Effects of the Invention] By carrying out the present invention as described above, firstly, the liquid phase oxidation reaction process of naphthalene can be achieved by producing 1,
In order to produce 4-naphthoquinone, high-purity THAQ can be produced in high yield and with high selectivity without the need for complicated purification steps in the Diels-Alder reaction and reduction reaction with 1,3-butadiene in the subsequent steps. can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet diagram showing one embodiment based on the present invention.

[Claims]

1. In a method for producing 1,4-naphthoquinone in which naphthalene is oxidized in a liquid phase using an acidic aqueous solution containing ceric ions, (a) an acidic aqueous solution containing ceric ions is electrolytically oxidized, and the A first step in which cerium ions are converted into second cerium ions and supplied to a second step. (b) Liquid-phase oxidation of naphthalene under ultrasonic irradiation using the acidic aqueous solution containing ceric ions obtained in the first step, and then an organic solvent that is immiscible with water and not oxidized to ceric ions. A second step of extracting 1,4-naphthoquinone using a solvent and separating an organic solvent phase from an acidic aqueous solution phase containing unreacted ceric ions and ceric ions produced by an oxidation reaction. (c) Naphthalene, 1,4-naphthoquinone and organic solvent are separated and purified from the organic solvent phase obtained in the second step to obtain 1,4-naphthoquinone as a product, while naphthalene and organic solvent are each separated and purified.