JPS5830287B2 - hydroquinone water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to producing an aqueous hydroquinone solution by acid decomposing para-diisopropylbenzene hydroperoxide (hereinafter referred to as "peroxide") obtained by oxidizing para-diisopropylbenzene.

The present inventors investigated an industrial method for separating and purifying a colorless and transparent hydroquinone aqueous solution from an acid decomposition reaction solution obtained by acid decomposing peroxide, and as a result, discovered a new method and found an industrial method to do so. have also invented a new and extremely effective method for producing hydroquinone.

In the present invention, peroxide obtained by oxidizing Baladi isopropylbenzene is brought into contact with an acid catalyst in a state in which it is dissolved in an organic solvent that dissolves it well, thereby carrying out an acid decomposition reaction, and converting the acid decomposition reaction liquid into an alkali. When neutralizing with an aqueous solution, the neutralization end point is kept at a low pH of 3.0 or less, and the organic solvent used for acid decomposition and acetone generated by acid decomposition of peroxide are distilled off, and the residual aqueous solution is distilled off. This is a method for producing a hydroquinone aqueous solution in which hydroquinone is obtained as an extracted residual aqueous solution by extracting and removing organic impurities contained therein from the residual aqueous solution using an organic solvent that is insoluble or poorly soluble in water.

Hydroquinone is produced by oxidizing isopropylbenzene to produce peroxide, which is then decomposed with acid to produce hydroquinone and acetone.Then, hydroquinone is separated as an aqueous solution by distillation and extraction, and hydroquinone crystals are obtained from this aqueous solution. The production method is the well-known hydroquinone production method.

However, in the case of the method for producing hydroquinone that involves the above steps, various by-products generated in the oxidation step inevitably mix with the peroxide, and these impurities undergo further chemical changes in the acid decomposition step. Therefore, various unidentified impurities are included in the acid decomposition reaction solution together with hydroquinone.

For this reason, the acid decomposition reaction solution is usually obtained as a blackish brown or reddish brown solution, and the hydroquinone crystals obtained from such a hydroquinone solution are also a contaminated reddish brown product. It has been virtually impossible to produce pure white, acicular hydroquinone crystals from the acid-decomposed solution using conventional purification and separation methods such as distillation, extraction, and crystallization.

However, most of the uses in which hydroquinone is consumed are;
Since it is used in fields such as photographic development and polymerization prevention of polymeric monomers, the requirements for quality are extremely strict, as seen in the JIS and ASA standards.

Therefore, it has hitherto been impossible to use hydroquinone produced by the above-mentioned production method in such fields unless it is decolorized using a large amount of activated carbon.

As a result of repeated detailed studies on the acid decomposition solution containing hydroquinone obtained by acid decomposition of peroxide, the present inventors found that organic impurities coexisting in the solution are insoluble in water at low pH. However, we discovered the surprising fact that when the pH is high, this becomes an aqueous solution, and when the acid decomposition solution is neutralized with an alkaline aqueous solution, the pH of the solution
3.0 or less, remove solvents such as acetone by distillation, extract the residual aqueous solution with an organic solvent such as benzene, and obtain hydroquinone as the extracted residual aqueous solution. In addition, we have established a method for producing an aqueous hydroquinone solution that can easily produce pure white, acicular hydroquinone crystals that can be used in any field.

In the present invention, the peroxide used is one obtained by oxidizing paradiisopropylbenzene as described above.

Although each step of the method of the present invention can be carried out batchwise, it is industrially advantageous to carry out the process continuously.

The solvent in the acid decomposition reaction may be any organic solvent as long as it dissolves peroxide, but since acetone is produced by acid decomposition of peroxide, it is industrially advantageous to use acetone. It's a method.

Peroxide is dissolved in acetone and used as a solution with a concentration of 10 to 30 weight percent.

The acid catalyst may be either a mineral acid or an organic acid, but sulfuric acid is preferred.

As the catalytic sulfuric acid, sulfuric acid with a concentration of 70 to 98% by weight that does not contain much water is dissolved in acetone, and the sulfuric acid concentration is 0.5.
An acetone solution of ~20 weight percent is used.

The acid decomposition reaction temperature is preferably kept constant at a predetermined temperature of 70° C. or lower.

Both peroxide and catalytic sulfuric acid solutions are continuously fed to the acid decomposition tank at a constant rate.

Preferably, the peroxide concentration in the acid decomposition tank is 10 to 30 weight percent, and the catalytic sulfuric acid concentration is 0.1 to 1.5 weight percent, assuming that it is not acid-decomposed.

After the acid decomposition reaction is completed, the acid decomposition solution is led to a neutralization tank and neutralized with an alkaline aqueous solution such as caustic soda, soda carbonate, or ammonia. remain in an incompletely neutralized state.

The concentration of the alkaline aqueous solution used for neutralization is 0.5 to 5. OX
Preferably, the weight percent.

When separating the neutralized salt, the alkaline aqueous solution concentration is 1.
Although it is desirable that the alkali concentration be 20% by weight or more, a lower alkali concentration is desirable in order to prevent crystal precipitation of hydroquinone in the subsequent distillation step.

Therefore, when using a highly concentrated alkaline aqueous solution, after separating and removing the neutralized salt by means such as filtration, sufficient water is replenished here to prevent the precipitation of hydroquinone crystals in the distillation process.

As long as the neutralization end point of the acid decomposition solution is below pH 3.0, there will be no problem with the quality of the hydroquinone finally obtained.
Industrially, it is preferable that the pH range is from 2.0 to 3.0 in order to avoid corrosion of equipment materials.

After neutralization, the acid decomposed solution is subjected to S distillation to remove acetone while maintaining its pH at a low level.

Hydroquinone is obtained as a distillation residual aqueous solution,
Since this aqueous solution still contains organic high-boiling point impurities, these are extracted and removed using an organic solvent such as benzene that is insoluble or sparingly soluble in water.

Hydroquinone is obtained as an extracted aqueous layer, that is, an aqueous solution.

The degree of coloring of the hydroquinone aqueous solution thus obtained was determined by setting the hydroquinone concentration to about 15% by weight and using a photoelectric colorimeter based on the light transmittance at a wavelength of 3500 m.

The present invention will be explained in more detail with reference to Examples below.

Of course, these Examples do not restrict the present invention in any way.

Example 1 Acetone solution obtained by oxidizing baradiisopropylbenzene was dissolved in acetone with a moisture content of 1.0% by weight to make an acetone solution of 19% by weight, and an acetone solution with a concentration of 98% by weight was prepared.
Concentrated sulfuric acid of weight percent was dissolved in acetone of the above water content, and an acetone solution with a sulfuric acid concentration of 2.7 weight percent was prepared at a flow rate of 2100 parts by weight/hour and 4.
The mixture was supplied to the acid decomposition tank at a rate of 85 parts by weight/hour, mixed and stirred uniformly, and the reaction temperature was maintained at 50±1°C.

The residence time was set to 1.5 hours, and the overflowing acid decomposition liquid was led to the neutralization tank, and a sodium carbonate aqueous solution with a concentration of 1.26 weight percent was supplied to the neutralization tank at a flow rate of 952 parts by weight/hour. The liquid was neutralized.

The neutralization solution is further adjusted to pH 2.5 with a small amount of the above sodium carbonate aqueous solution.
After finely adjusting the acetone, the acetone is completely distilled off from the neutralized solution using a batch distillation apparatus, and about 1% of the acetone is added to the resulting residual aqueous solution.
73 parts by weight of benzene was added, the liquid temperature was adjusted to 65°C, and 30 parts by weight was added.
After stirring and mixing vigorously for a minute, the mixture was allowed to stand still for 5 minutes, and the lower aqueous phase was separated.

Benzene was added to the single aqueous phase, and the same operation was repeated twice to obtain a benzene extracted and separated aqueous solution.

Hydroquinone in this aqueous solution was chemically analyzed by the method of JIS-8738, and a hydroquinone concentration of 14.83 weight percent was obtained.

The light transmittance of this aqueous solution at a wavelength of 350 nm measured by a photoelectric colorimeter "Electronics-20'" manufactured by Shimadzu-Bausch & Lomb was 13.5%.

This light transmittance shows a very small value for an aqueous solution with a high degree of coloring, and a high value for an aqueous solution with a low degree of coloring, that is, a highly purified aqueous solution, and those with a transmittance of 20% or less are reddish brown.

In addition, when measuring the light transmittance of each wavelength of a hydroquinone aqueous solution obtained by the same method as in the example using distilled water as a comparison sample in the visible light range of wavelengths 320 to 800 nm, the wavelength at which the light absorption is maximum was determined. was around 350 nm.

(Figure-1) Example 2 A caustic soda aqueous solution with a concentration of 290% by weight was supplied at a rate of 350 parts by weight/hour to the acid decomposed liquid obtained by acid decomposition in the same manner as in Example 1, and the neutralized liquid was After finely adjusting the pH to 20 and separating the produced Glauber's salt by filtration, water was replenished at a ratio of about 20 parts by weight of distilled water to 100 parts by weight of this solution, and in the same manner as in Example 1, acetone was distilled off. Benzene extraction was performed to obtain an aqueous solution having a hydroquinone concentration of 14.85% by weight.

The transmittance at a wavelength of 350 nm measured by a photoelectric colorimeter is 1
It was 6.2%.

Hereinafter, in the same manner as in Examples 1 and 2, p
Experiments were conducted with various amounts of H, and aqueous solutions were obtained for each.

The light transmittance of these aqueous solutions at a wavelength of 350 nm and p
The relationship of H was as shown in Figure 2.

In addition, those having a pH of 3.0 or more are described as comparative examples.

[Brief explanation of the drawing]

FIG. 1 is a light transmission curve diagram obtained by measuring the light transmission of an aqueous solution having a hydroquinone concentration of 15±0.3 weight percent in the visible light range (320 to 800 nm) obtained by the same method as in Examples. In Figure 2, the vertical axis represents the light transmittance at a wavelength of 350 nm of a benzene extracted and separated aqueous solution obtained in the same manner as in the example, and the horizontal axis represents the pH of the acid-decomposed and neutralized solution.

Claims (1)

[Claims] 1 The acid decomposition reaction solution of para-di-isopropylbenzene hydroperoxide obtained by oxidizing para-di-isopropylbenzene is neutralized with an alkaline aqueous solution, then acetone is distilled off, and organic impurities are removed from the remaining aqueous solution with an organic solvent. 1. A method for producing a hydroquinone aqueous solution, which comprises maintaining the end point of the neutralization at pH 3.0 or lower in producing the hydroquinone aqueous solution by extracting and removing components.