JPH013149A - Method for producing hydroxybenzoic acid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention aims to improve the production method of hydroxybenzoic acid, and more specifically, to improve the production method of hydroxybenzoic acid, and more specifically, to improve the production method of hydroxybenzoic acid, and more specifically, to improve the production method of hydroxybenzoic acid. The present invention relates to a method for safely and efficiently producing p-hydroxybenzoic acid useful as a raw material.

[Conventional technology]

In general, hydroxybenzoic acid is produced by the so-called Kolpel 213 reaction, in which a carboxyl group is introduced into a benzene ring by reacting carbon dioxide with an alkali metal salt of phenol. To recover hydroxybenzoic acid from this reaction mixture, water is usually added to the reaction mixture to separate the alkali metal salt of hydroxybenzoic acid as an aqueous solution, and then a mineral acid is added to this aqueous solution to recover the hydroxybenzoic acid. This is done by precipitating benzoic acid. By the way, the mother liquor after acid precipitation separation of hydroxybenzoic acid in this way contains a large amount of alkali metal salts of mineral acids, and various methods have been proposed for recovering and reusing them. ing.

For example, sulfite residue is passed through an aqueous solution containing p-hydroxybenzoic acid dipotassium salt, acid precipitated, and p-hydroxybenzoic acid is filtered off. Phenol and lime are added to the mother liquor to remove potassium from the phenol solution. (Japanese Patent Publication No. 40-3767), hydroxybenzoic acid and alkali metal hydroxide are simultaneously recovered by treating an aqueous hydroxybenzoic acid alkali salt solution with activated carbon and then electrodialyzing it using an ion exchange membrane. How to get (
(Japanese Patent Publication No. 40-11492), etc.; the former is a phenol-potassium aqueous solution that contains impurities and has a low concentration, so in order to use it as a raw material for the Kolbe-Schmidt reaction, it must be purified, Drying requires a large amount of cost and energy, and the latter requires the use of dilute solutions during electrodialysis, resulting in large dissolution losses of hydroxybenzoic acid and recovery of alkali metal hydroxide. However, these methods required a great deal of cost and energy, and were unsuitable for industrial implementation.

On the other hand, after distilling off unreacted phenol from the reaction mixture of the Colchen-Humit reaction, water was added thereto to dissolve it, and then hydrochloric acid was added to precipitate hydroxybenzoic acid.
A method has also been proposed in which chlorine is blown into the acid precipitation mother liquor after filtration, the generated sparingly soluble chlorine compounds are removed, and the residual solution is electrolyzed to recover alkali metal hydroxides (Japanese Patent Publication No. 1973).
This method has many drawbacks as an industrial method, such as not only the recovery rate is not very high, but also hygienic problems due to the use of toxic chlorine, and equipment and equipment are easily corroded. are doing.

[Problem that the invention seeks to solve]

The present invention utilizes alkali metal hydroxide, which can be recycled and reused in the production process of the alkali metal salt of phenol, which is the raw material, from the acid precipitation mother liquor produced as a by-product when producing hydroquine benzoic acid by the Kolbe-Schmidt reaction. This work was developed with the aim of providing a method that can be obtained with a high recovery rate without using such toxic substances.

[Means for solving problems]

The present inventors have conducted extensive research in order to develop a method for simply and efficiently recovering alkali metal hydroxide from the acid precipitation mother liquor produced during the production of hydroxybenzoic acid by the Kolbe-Schmidt reaction =3= As a result, it was discovered that the objective could be achieved by treating the acid precipitation mother liquor with a reverse osmosis membrane instead of treating it with chlorine, and then electrolytically treating the treated solution.Based on this knowledge, the present invention was accomplished. Ta.

That is, the present invention provides a method for producing hydroxybenzoic acid by reacting carbon dioxide with an alkali metal salt of phenol obtained by reacting phenol with an alkali metal hydroxide. The alkali metal salt of is separated as an aqueous solution, from which hydroxybenzoic acid is precipitated and recovered by acid precipitation, and the mother liquor is subjected to reverse osmosis membrane treatment and electrolytic treatment to produce caustic alkali, which is then combined with phenol. The present invention provides a method for producing hydroxybenzoic acid, which is characterized in that it is recycled and reused for reaction.

In the present invention, the reaction between phenol and alkali metal hydroxide may be carried out in such a manner that, for example, the reaction between phenol and alkali metal hydroxide is 0.1 to 1
Add 0 mol preferably 0.5 to 2 mol of alkali metal hydroxide, -10°C to 200°C 1 preferably 15 to 1
This can be carried out by reacting in a temperature range of 00°C. In this reaction, the above-mentioned two may be mixed and reacted instantly, or may be reacted over 0.01 to 10 hours. As the alkali metal hydroxide, thorium hydroxide or potassium hydroxide is usually used.

This reaction may be carried out by reacting phenol and alkali metal hydroxide in an anhydrous state, or by forming an aqueous solution having a total concentration of 90% by weight or less, preferably 15 to 50% by weight of alkali metal hydroxide. It can also be carried out by reacting with phenol. The alkali metal salt of phenol thus obtained is then subjected to distillation to remove water therein, and at this time, excess 7 enols can also be removed at the same time.

When this alkali metal salt of phenol is used in the next reaction with carbon dioxide, it must be in a substantially anhydrous state, but it is fine even if it contains unreacted alkali metal hydroxide or phenol. can not use.

The next reaction between the alkali metal salt of phenol and carbon dioxide is well known as the Kolbe-Schmits reaction, and is an example of the reaction between the alkali metal salt of phenol and carbon dioxide. It can be done by In this case, when the sodium salt is used as the alkali metal salt of phenol, 0-hydroxybenzoic acid, that is, salicylic acid is obtained, and when the potassium salt is used, p-hydroxybenzoic acid is obtained.

This reaction converts the alkali metal salt of phenol into 100 to 3
This can be carried out by maintaining the temperature at 00°C, preferably 160 to 260°C, and passing carbon dioxide in the form of a scum. At this time, if necessary, the reaction can be accelerated by applying pressure up to 100 kg/cm2. Carbon dioxide is supplied until the carboxylation of the alkali metal salt of phenol is fully completed, and usually, it is sufficient to use less than 100 moles, preferably less than 50 moles, per mole of the alkali metal salt of phenol. The reaction time is 0.0
The normal time is about 0.01 to 10 hours.

At this time, it is advantageous to use a solvent that is immiscible with water in order to improve the reaction efficiency and facilitate the subsequent hydroxybenzoic acid separation operation. Such solvents include
For example, hydrocarbon solvents such as light oil, kerosene, benzene, toluene, and xylene, and ether solvents such as diethyl ether and dipropyl ether are suitable. Also, at this time,
The coexistence of free phenol is advantageous because an alkali metal salt of phenol is generated from the generated alkali metal salt of hydroxybenzoic acid and an excess amount of phenol, and this salt reacts with carbon dioxide to promote carboxylation.

There is no particular limit to the amount of the above solvent, but usually
It is used in an amount about 1 to 10 times that of the alkali metal salt of phenol.

The reaction mixture obtained by the reaction of the alkali metal salt of phenol and carbon dioxide contains the unreacted alkali metal salt of phenol of the alkali metal salt of hydroxybenzoic acid, phenol, and a solvent. The components are transferred to the aqueous phase and separated from the solvent phase. The amount of water added in this case is selected within the range of 0.1 to 10 times the amount of the reaction mixture, preferably 0.3 to 5 times the amount of the reaction mixture.

The aqueous phase thus separated contains an alkali metal salt of hydroxybenzoic acid, an alkali metal salt of phenol,
Since it contains phenol, the phenol is extracted and removed using an aromatic hydrocarbon solvent such as toluene or xylene, and then mineral acid is added in a conventional manner to precipitate hydroxybenzoic acid. The mineral acids used in this case include hydrochloric acid, sulfuric acid, nitric acid, etc., and hydrochloric acid is particularly preferred. This mineral acid contains 0.1 to 500 parts of mineral acid per 100 parts by weight of the aqueous phase.
It may be added in parts by weight as an aqueous solution with a concentration of 1 to 80% by weight.

By this acid precipitation treatment, hydroxybenzoic acid precipitates as crystals, which are separated and recovered by means such as filtration and centrifugation.

In the method of the present invention, it is important to recover alkali metal hydroxide from the acid precipitation mother liquor after hydroxybenzoic acid has been separated in this manner by reverse osmosis treatment and electrolytic treatment. This reverse osmosis treatment uses a cellulose acetate membrane or an aromatic polyamide membrane, which are commonly used as semipermeable membranes for reverse osmosis, at a temperature of 0 to 100°C, preferably 10 to 45°C.
It can be carried out according to a conventional method at a temperature of . At this time, pressure may be applied as desired to increase the permeation rate.

Next, one example of a preferred embodiment of this reverse osmosis treatment will be described with reference to the accompanying drawings. The figure is an explanatory diagram of the main parts of the reverse osmosis treatment equipment.
is continuously supplied to the supply zone 3 of the processing tank. Then, a part of the aqueous solution containing only the alkali metal salt from the acid precipitation mother liquor passes through the semipermeable membrane 5 and moves to the separation zone 4, and the rest is returned to the tank 1 again. In this way, an aqueous solution containing only the alkali metal salt can be continuously taken out from the separation zone 4.

As an apparatus for carrying out the reverse osmosis treatment of the present invention, any type of apparatus can be used, such as a flat membrane type, a spiral wound type, a tubular structure type, and a hollow fiber membrane type.

The aqueous alkali metal salt solution obtained from the acid precipitation mother liquor by reverse osmosis treatment is adjusted to a concentration in the range of 12 to 36% by weight, and then subjected to electrolytic treatment. This electrolytic treatment is carried out using an ion exchange membrane such as Nafion membrane under the same conditions as in the production of alkali metal hydroxide salts by the general ion exchange membrane method. Using platinum, sliding voltage 1-5V/cel
1, a cathode current density of 10 to 50 A/+] m2, and an electrolyte temperature of 0 to 100°C.

As a result of such electrolytic treatment, an aqueous alkali metal hydroxide solution is produced, which has sufficient purity to be used for the production of alkali metal salts of phenol, so it can be used as is or after concentration as desired. , recycled to the reaction step with phenol.

〔Effect of the invention〕

According to the present invention, alkali metal hydroxide can be recovered at a high recovery rate of 99% from the acid precipitation mother liquor produced during the production of hydroxybenzoic acid by the Kolbe-Schmidt reaction, without using toxic substances such as chlorine. I can do it,
Moreover, since this can be recycled and reused in the preparation of an alkali metal salt of phenol, an efficient and safe industrial method for producing hydroxybenzoic acid can be provided.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example: Into an autoclave equipped with a stirrer, 57.66 g of 50% potassium hydroxide aqueous solution and 53.4 h of phenol were charged, pressure IQ - 15 mmHg, temperature +00 - 150°.
6 g of potassium phenolate, ogg, was obtained by reacting the mixture while stirring and distilling off water and unreacted phenol.

Next, return the inside of the autoclave to normal pressure and use light oil 272.22
g and 33.969 g of phenol were added, the inside of the autoclave was replaced with nitrogen, carbon dioxide was introduced to a pressure of 5 kg/cm2 at a temperature of 230°C, and the reaction was allowed to proceed for 10 minutes without stirring. After the reaction was completed, the temperature was cooled to 80°C, 0ml of water was introduced, and after mixing well, it was separated into a light oil layer and an aqueous layer using a separatory funnel, and the aqueous layer was diluted with toluene 50°C.
It was extracted three times with mQ each to remove unreacted phenol.

After the extraction operation, 44.3 mu of concentrated hydrochloric acid was added to the aqueous layer, and the precipitated crystals were filtered out, yielding 37.19 mu of p-hydroxybenzoic acid.
and 0.71 g of salicylic acid were obtained.

This filtrate was subjected to reverse osmosis treatment using the apparatus shown in the figure, which was equipped with a semipermeable membrane (crosslinked polyamide composite membrane: Toshi Co., Ltd., trade name 5ll-2105, membrane thickness 300A). At this time, the rejection rate of potassium chloride was 5%, and the rejection rate of organic matter was almost 100%.

The purified potassium chloride aqueous solution was subjected to electrolysis to recover potassium hydroxide. That is, electrolysis was carried out using a Nafion membrane as an ion exchange membrane, carbon as an anode, and platinum as a cathode at a cathode current density of 30 A/dm3, a voltage of 4.2 V/ce11, and an electrolysis temperature of 80°C. Potassium hydroxide recovery rate is 99
%Met.

Comparative Example 1 Same as Example, 386g of phenol = 1 in autoclave
2- Add 472 g of 50% potassium hydroxide aqueous solution and
The reaction is carried out under a reduced pressure of -15 mmHg with stirring at +00-150°C, and water and unreacted phenol are completely distilled off. Next, the pressure was returned to normal pressure, carbon dioxide was introduced at 200 to 230°C, and the reaction was carried out for about 1 hour, and then the pressure was reduced to distill off the by-product phenol. After repeating this operation three times and distilling off a total of about 1,909 g of by-product phenol, 448 g of the resulting reaction product was dissolved in 10,009 g of water, decolorized using activated carbon and zinc dust, and then 350 g of 35% hydrochloric acid.
The pH was adjusted to 3.0 using g and the precipitated p-hydroxybenzoic acid was filtered off. The yield at this time was 270g, and the purity was 99.
The yield was 95%. Separately, 1500 g of acid precipitation mother liquor was obtained. This mother liquor contains 0.0% p-hydroxybenzoic acid.
4%, salicylic acid 0.2%, potassium chloride 20.0%,
It contains trace amounts of iron and zinc. This acid precipitation mother liquor +o
When oog is placed in a flask equipped with a stirrer and a reflux condenser and chlorine is blown into the flask at 70°C, a reaction occurs and chlorides are produced, which are successively removed from the bottom. The reaction was complete in 3 hours and chlorine 269 was absorbed. After cooling the reaction solution to 30°C and removing residual chloride,
% potassium hydroxide was added and the resulting precipitate was filtered off. Total amount of chlorinated substances removed is approximately 15g (dry state)
Dea Iko.

Using the potassium chloride aqueous solution thus obtained, carbon was used as an anode, mercury was used as a cathode, cathode current density was 30 A/dm3, voltage was 4.2 V, and electrolyte temperature was 70°C.
1 Electrolysis was carried out at an amalgam concentration of 0.2%, and the resulting amalgam was dissolved with an appropriate amount of water to recover 50% potassium hydroxide. The recovery rate was 70%.

[Brief explanation of the drawing]

The figure is an explanatory diagram of a reverse osmosis treatment apparatus suitable for use in the present invention. In the figure, numeral 1 is a tank, 2 is a pump, and 5 is a semipermeable membrane. Procedural amendment July 12, 1988 Director General of the Patent Office Yoshi 1) Moon Takeshi l, case indication 1988 Patent Application No. 157140 2, name of invention Process for producing hydroxybenzoic acid 3, person making amendment case Relationship with Patent applicant: 3-1-1 Marunouchi, Chiyoda-ku, Tokyo, Idemitsu Petrochemical Co., Ltd. Representative: Mutsumi Hongo 4, Agent: 5, Date of amendment order: Voluntary order: 6, Number of inventions increased by amendment: 08, Contents of correction (1) "Reverse osmosis treatment" in the second to bottom line of page 9 of the specification is corrected to [Reverse osmosis membrane treatment j]. (2) "Reverse osmosis treatment" in the 1st, 7th, and 8th lines, the bottom four lines, and the bottom line of the same page 10 is replaced with "reverse osmosis membrane treatment"
I will correct it. (3) “Reverse osmosis treatment” on page 13, line 10
Corrected to "reverse osmosis membrane treatment." (4) rV/cell on the 4th line from the bottom of page 13
Correct it to "rV/cell". (5) Change “reverse osmosis treatment” in line 13 of page 15 to “
Corrected to "reverse osmosis membrane treatment."

Claims (1)

[Claims] 1. In a method for producing hydroxybenzoic acid by reacting carbon dioxide with an alkali metal salt of phenol obtained by reacting phenol with an alkali metal hydroxide, the alkali metal salt of hydroxybenzoic acid is extracted from the reaction mixture with carbon dioxide. is separated as an aqueous solution, hydroxybenzoic acid is precipitated and recovered by acid precipitation of this aqueous solution, and the mother liquor is subjected to reverse osmosis membrane treatment and electrolytic treatment to generate alkali hydroxide, which is then reacted with phenol. 1. A method for producing hydroxybenzoic acid, which is characterized in that it is recycled and reused for commercial purposes.