JPH0529341B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> The present invention provides an industrially advantageous method for producing 1,4-naphthoquinone by liquid phase oxidation of naphthalene using an acidic aqueous solution containing ceric ions. Regarding. 1,4-naphthoquinone is industrially useful as a raw material for anthraquinone.

<Prior Art> A method for producing 1,4-naphthoquinone by liquid-phase oxidation of naphthalene using an acidic aqueous solution containing ceric ions is well known. For example, there is a method for producing 1,4-naphthoquinone by oxidizing naphthalene dissolved in an organic solvent that is immiscible with water using a ceric ion-acid aqueous solution (Japanese Patent Publication No. 34978/1983), There is a method for producing 1,4-naphthoquinone characterized by suspending it in an aqueous solution of a ceric salt using a dispersant (Japanese Patent Application Laid-open No. 1983-61321).
As acidic aqueous solutions containing ceric ions used in these oxidation reactions, cerium ammonium nitrate-nitric acid aqueous solutions and cerium sulfate-sulfuric acid aqueous solutions are generally used. Further, in the conventional oxidation reaction using ceric ions, the temperature is usually preferably 40 to 80°C.

Then, from the obtained liquid phase oxidation product, 1,4-
As a method for separating and purifying naphthoquinone, methods such as concentrating the solvent, filtering, washing, and recrystallization are generally performed.

Further, the liquid phase oxidation reaction process usually includes an electrochemical regeneration process for regenerating cerium ions produced after the liquid phase oxidation reaction into cerium ions.

<Problems to be Solved by the Invention> In the conventional method for producing 1,4-naphthoquinone by liquid phase oxidation using an acidic aqueous solution containing ceric ions, normally It is advantageous that the higher the concentration of 2cerium ions or the higher the oxidation reaction temperature, the faster the reaction rate becomes. On the other hand, from the viewpoint of selectivity for the target 1,4-naphthoquinone, it is important that the concentration of ceric ions in the acidic aqueous solution containing ceric ions is low, or that the oxidation reaction temperature is low. is preferred. In addition, when a sulfuric acid aqueous solution of ceric sulfate is used as the acidic aqueous solution containing ceric ions, the solubility of cerous sulfate produced by the oxidation reaction with ceric sulfate is low, so the sulfuric acid aqueous solution However, when a nitric acid aqueous solution of ceric ammonium sulfate is used, the solubility of ceric ammonium nitrate is high, resulting in a slow reaction rate. Although this method is advantageous, it has disadvantages in terms of selectivity and the production of large amounts of by-products. Therefore, from an industrial perspective, acidic aqueous solutions containing ceric ions are considered as a compromise between productivity by increasing the reaction rate and complexity of the purification process and product quality by selectivity of 1,4-naphthoquinone. Conditions such as the type of cerium ion, the concentration of ceric ions, and the oxidation reaction temperature are set. Moreover, if the temperature is too high, hydrolysis of the ceric salt occurs, which is disadvantageous in terms of coloration of the product and corrosion of the equipment. As a result of these, as mentioned above, the oxidation reaction temperature is usually preferably 40 to 80°C.

Next, in order to purify the produced 1,4-naphthoquinone, methods such as simply concentrating the solvent, filtering, and washing do not sufficiently remove unreacted naphthalene and byproducts, making it impossible to obtain a product of satisfactory purity. However, recrystallization is essential, which complicates the process and unavoidably lowers the yield.

Furthermore, the recovered acidic aqueous solution containing cerous ions is electrolytically oxidized to convert the cerous ions into secondary cerium ions.
In the case of regenerating cerium ions, 1,4-naphthoquinone dissolved in the acidic aqueous solution causes a decrease in current efficiency in electrolytic oxidation and a decrease in electrode life. Therefore, when recovering an acidic aqueous solution containing cerous ions, it is necessary to ensure that 1,4-naphthoquinone is not substantially contained therein.

The present invention solves the above-mentioned drawbacks and can accelerate the reaction rate even when the concentration of ceric ions is low. As a result, the selectivity of the target product can be increased and the produced 1 , 4-naphthoquinone to obtain high purity products.

<Means for Solving the Problems> As a result of intensive study on the shortcomings of the conventional method, the present inventors have developed a method for obtaining 1,4-naphthoquinone by oxidizing naphthalene using an acidic aqueous solution containing ceric ions. By carrying out the liquid phase oxidation reaction under ultrasonic irradiation, the reaction rate is accelerated even at low reaction temperatures or at low concentrations of ceric ions, and 1,4-naphthoquinone is selected. I found out that it can be obtained with good performance. Furthermore, as a result of repeated studies on the organic solvent used to extract 1,4-naphthoquinone from the liquid phase oxidation reaction and the method for separating and purifying 1,4-naphthoquinone, the present invention was completed. That is, the present invention provides (a) electrolytic oxidation of an acidic aqueous solution containing cerous ions, converting the cerous ions in the aqueous solution into ceric ions, and supplying the first step to the second step of the agent.
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 immiscible with water and not oxidized to ceric ions. A second step of extracting 1,4-naphthoquinone using an organic solvent and separating the organic solvent phase from an acidic aqueous phase containing unreacted ceric ions and cerous ions generated by the oxidation reaction; ) Naphthalene, 1,4-naphthoquinone and the 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 the organic solvent are each recovered and used in the first step. This is a method for producing 1,4-naphthoquinone characterized by comprising a third step of returning it to 1,4-naphthoquinone. This will be explained in detail below.

As the acidic aqueous solution containing ceric ions used in the first step of the present invention, various acidic aqueous solutions of various ceric salts such as ceric ammonium nitrate, ceric nitrate, or ceric sulfate can be used. As the acid, an acid corresponding to the anion forming the above-mentioned cerium ion source can be used, but other acids can also be added. For example, sulfuric acid, sulfuric acid, etc. can be used alone or in combination. can be used. This step mainly has the role of regenerating the cerous ions generated in the liquid phase oxidation of naphthalene in the second step and supplying them again to the second step. It also has the role of oxidizing into ions and supplying them to the second step. Electrolytic oxidation can be performed using conventional methods.

The obtained acidic aqueous solution containing ceric ions is supplied to the second step and used in the liquid phase oxidation reaction of naphthalene. Here, the ceric ion concentration in the acidic aqueous solution is preferably 0.05 to 6 mol/,
More preferably it is in the range of 0.1 to 3 mol/.
If the concentration is too low, the oxidizing power will be weak, which will not only slow down the reaction rate but also increase the amount of reaction liquid, which is disadvantageous. On the other hand, if it is too high, the above-mentioned problems and the viscosity of the liquid may increase, which may interfere with various process operations. Regarding the acid concentration in the oxidizing aqueous solution, if the acid concentration is too low, the ceric ions will become unstable, and if the acid concentration is too high, the solubility of the ceric ions will decrease and the equipment will be corroded. Due to this disadvantage, the acid concentration in the acidic aqueous solution is preferably between 0.3 and 10 mol/, more preferably between 0.7 and 2.0 mol/.

In the present invention, the liquid phase oxidation reaction in the second step is performed under ultrasonic irradiation. In conventional methods, the liquid phase oxidation reaction is usually carried out under forced stirring using a stirrer, external circulation, gas blowing, etc., but in the present invention, it is carried out under ultrasonic irradiation, preferably in combination with forced stirring. Even if the reaction temperature is low or the concentration of ceric ions is low, a sufficient reaction rate can be maintained. As a result, the second
The liquid phase oxidation reaction of the step is preferably carried out at 0 to 80°C, more preferably at 15 to 35°C. At temperatures above 80°C, problems may arise from the aforementioned hydrolysis of the ceric salt, contamination and coloring of side reaction products, and corrosion of the equipment, while at temperatures below 0°C, the reaction rate may be reduced. In addition to this, cooling costs are incurred. More advantageously, by performing the reaction at 15 to 35°C, 1.
The selectivity of 4-naphthoquinone can be increased. The ultrasonic waves used in the present invention may have a frequency of 10 KHz or higher, and the irradiation method may be either an external irradiation method or an internal irradiation method,
Further, devices having individual frequencies and outputs can be used as the ultrasonic generator, and the ultrasonic radiator may be of any type such as a flat plate type, ring type, or disk type.

Examples of organic solvents that are immiscible with water and are not oxidized to ceric ions used in the second step of the present invention include aromatic hydrocarbons such as benzene, tert-butylbenzene, and chlorobenzene, or substituted substances thereof, and cyclohexane. , n-hexane,
Examples include organic solvents such as aliphatic hydrocarbons such as n-pentane and n-octane, and chlorinated aliphatic hydrocarbons such as carbon tetrachloride, chloromethyl, and dichloroethane. These organic solvents include naphthalene and 1,
In the operation of thoroughly dissolving 4-naphthoquinone and extracting and separating the organic solvent phase and the acidic aqueous solution phase after the second step, the concentration of 1,4-naphthoquinone in the acidic aqueous solution phase is reduced. The ceric ions generated by the oxidation reaction contained in the acidic aqueous solution phase are electrolytically oxidized in the first step, regenerated into ceric ions, and recycled for use. The presence of 1,4-naphthoquinone substantially eliminates problems such as a decrease in current efficiency during electrolytic oxidation and a decrease in electrode life.

When naphthalene is oxidized with an acidic aqueous solution containing ceric ions, the naphthalene can be dissolved in these organic solvents and oxidized, or the naphthalene can be oxidized without using a solvent and an organic solvent can be added afterwards. The product 1,4-naphthoquinone may be dissolved in an organic solvent, and the system may be in the form of a liquid or a slurry.

In the third step of the present invention, naphthalene, 1,4-naphthoquinone and the organic solvent are separated and purified from the organic solvent phase obtained in the second step to obtain 1,4-naphthoquinone as a product. are collected and returned to the second step.

As a method for separating and purifying naphthalene, 1,4-naphthoquinone and the organic solvent from the organic solvent phase, conventional methods can be used. However, steam distillation under reduced pressure utilizing the vapor pressure difference between the organic solvent, naphthalene, and 1,4-naphthoquinone in the organic solvent phase is a preferred method because each component can be easily separated. By steam distillation, the organic solvent and naphthalene are almost completely removed, and highly pure 1,4-naphthoquinone can be obtained. Of course, washing and recrystallization may be performed to further increase purity. On the other hand, the organic solvent and naphthalene are recovered, returned to the second step, and reused.

The following description will be made based on a flow sheet diagram (FIG. 1) showing an embodiment in which the method of the present invention is carried out continuously from the first step to the third step.

<Second Step> Naphthalene is charged from the naphthalene tank 13 via line 35, and anolyte is charged from the anolyte tank 3 via line 18 to the reactor 4, and a liquid phase oxidation reaction is performed under ultrasonic irradiation. The reaction mixture is then passed through line 1
9 and into an extraction tower 5, where the 1,4-naphthoquinone in the reaction mixture is extracted using the organic solvent introduced from the solvent tank 7 through line 30. The organic solvent phase in which 1,4-naphthoquinone is dissolved passes through line 20 to distillation column 6, while the first
The acidic aqueous phase containing cerium ions is line 21
The anolyte is sent to the anolyte tank 3.

<Third Step> The organic solvent phase in which 1,4-naphthoquinone is dissolved is first concentrated in a distillation column 6 to such an extent that naphthalene dissolved in the organic solvent phase does not precipitate. The distilled organic solvent is cooled by a heat exchanger 22 and collected into a solvent tank 7. Distillation may be carried out at normal pressure, but since 1,4-naphthoquinone deteriorates at 80 to 90°C, it is preferable to distill under reduced pressure depending on the solvent used. Next, water is added to the distillation column 6 from the pure water tank 12 via the line 34 to perform steam distillation. The fraction is cooled by a heat exchanger 22 and stored in a separation tank 11, where it is separated into an aqueous phase and an oil phase consisting of naphthalene and an organic solvent. The aqueous phase is collected into the pure water tank 12 via line 33, and the oil phase is collected into the naphthalene tank 13 via line 32.

Naphthalene and organic solvents can be almost completely removed by steam distillation, yielding highly pure 1,4-naphthoquinone.
The 4-naphthoquinone crystals can also be washed with a fresh organic solvent in a filter 8 and dried in a drier 10 to produce a product.

<First step> The electrolytic cell 2 is equipped with an ion exchange membrane diaphragm in the center, which separates an anode chamber and a cathode chamber. An acidic aqueous solution containing cerium ions is introduced from the anolyte tank 3 into the anode chamber of the electrolytic cell 2 via line 16, and is introduced into the anolyte tank 3 via line 17.
circulates. On the other hand, a catholyte consisting of an electrolyte solution is supplied from a catholyte tank 1 to an electrolytic tank 2 through a line 14.
is introduced into the catholyte chamber of the catholyte chamber and circulated to the catholyte tank 1 via line 15. Electricity is passed through the electrolytic bath 2 to electrolytically oxidize the first cerium ions to the second cerium ions.

In the case of Figure 1, only one anolyte tank is installed, but it is also possible to install two anolyte tanks and store the liquid before electrolytic oxidation and the liquid after electrolytic oxidation in separate tanks. .

<Example> Next, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Platinum-plated titanium electrode for anode, SUS for cathode
A sulfuric acid aqueous solution of ceric sulfate was electrolyzed in a two-chamber electrolytic cell separated by an ion exchange membrane at a current density of 15 A/dm ² using a 316L electrode. The ceric ion concentration in the obtained sulfuric acid aqueous solution was 0.20 mol/.

Aqueous sulfuric acid solution containing this ceric ion
88680Kg and 300Kg of naphthalene dissolved in 517Kg of cyclohexane were charged into a reactor, internally irradiated with 28KHz, 400W ultrasonic waves, and reacted at 25°C for about 40 minutes. The reaction mixture was sent to an extraction column and cyclohexane
Using 12990Kg, undissolved 1,4-naphthoquinone was dissolved, and 1,4-naphthoquinone dissolved in the aqueous phase was dissolved.
4-naphthoquinone was extracted. The cyclohexane phase was sent to a distillation column, distilled under reduced pressure at 60°C and 400 mmHg, concentrated approximately 50 times, and then subjected to steam distillation at 60°C and 150 mmHg. Steam distillation was completed when 180 kg of water had been added.

Next, the remaining 1,4-naphthoquinone crystals were sent to a dryer and dried at 80° C. and 300 mmHg for 3 hours to obtain 342.9 kg of crystals with a purity of 99.2%.

[Brief explanation of drawings]

FIG. 1 is a flow sheet diagram showing an embodiment in which the method of the present invention is carried out continuously from the first step to the third step.

[Claims]

1 With ^the general formula R ¹ The organic halide represented by the general formula R ¹ COCOOH (R ¹ is the same as above) is reacted with water and carbon monoxide in the presence of a basic inorganic compound and a palladium-containing catalyst. Method for producing α-keto acids.

Claims (1)

The third step is to collect the water and return it to the second step. A method for producing 1,4-naphthoquinone, characterized by comprising: 2. The method according to claim 1, wherein in the third step, the operation of separating and purifying naphthalene, 1,4-naphthoquinone, and the organic solvent from the organic solvent phase is performed by steam distillation.