JPH0676671B2 - Method for producing m-hydroxybenzyl alcohol - Google Patents

Description

TECHNICAL FIELD The present invention relates to m-hydroxybenzyl alcohol (hereinafter, referred to as
(abbreviated as m-HBOH).

Although m-HBOH is a compound useful as an intermediate for industrial drugs or agricultural chemicals, at present, it has not been industrially supplied by an inexpensive manufacturing method thereof.

As a conventional method for synthesizing m-HBOH, there are a fermentation method using m-cresol as a raw material, reduction and hydrogenation reaction with sodium amalgam, NaBH ₄ , LiAlH _{4 and the} like using m-hydroxybenzaldehyde as a raw material. It has not been put to practical use due to insufficient yield. Further, the hydrogenation reaction is a reaction under high temperature and high pressure, and there are various problems in the industrial production method.

Regarding the method using m-hydroxybenzoic acid (hereinafter abbreviated as m-HBA) as a raw material, a reduction method using sodium amalgam and an electrolytic reduction method (Berichte 38 1752
(1905) has been proposed, but the yield was low and it could not be an industrial method.

The present inventors previously studied a method for producing m-HBOH,
We have already found a method for electrolytically reducing m-HBA in an aqueous solution or in a water-soluble organic solvent, and further adding a supporting electrolyte to the catholyte to obtain m-HBOH in high yield (JP 60-234987, JP-A-60-243293).

Problems to be Solved by the Invention The present inventors further diligently studied the industrial production method of m-HBOH, and electrolytically reduced m-HBA in an acidic aqueous solution to perform high-yield and high-purity m-HBOH. First proposed a method of obtaining
60-263858 (Japanese Patent Publication No. 63-47791), Japanese Patent Application No. 60-272467 (Japanese Patent Publication No. 63-47792)).

However, since this electrolysis reaction is carried out in an acidic aqueous solution, decomposition of acid-labile m-HBA is unavoidable during the reaction (Japanese Patent Application No. 60-272467).

These decomposition products are insoluble in water solvent and accumulate in the electrolytic cell as the reaction continues, and some of them are attached to the surface of the electrode and reduce the activity of the electrode. Aggravate. As a result, the production efficiency is lowered. Therefore, in order to efficiently carry out this electrolytic reduction reaction for a long period of time, it is important to promptly restore the activity of the electrode.

An object of the present invention is to provide a method for recovering the activity of an electrode in order to efficiently perform an electrolytic reaction for a long period of time.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and when the current efficiency has decreased, the accumulated m-HBA decomposition product is dissolved, washed and removed. The inventors have found that the current efficiency is improved and completed the present invention.

That is, the present invention is characterized in that, in the reaction of electrolytically reducing m-hydroxybenzoic acid in an acidic aqueous solution to obtain m-hydroxybenzyl alcohol, the inside of the electrolytic cell is washed with an alcohol solvent after completion of the electrolytic reaction. -A method for producing hydroxybenzyl alcohol.

Hereinafter, the present invention will be described in detail.

In the present invention, the acidic aqueous solution is not particularly limited as long as it is an acidic substance which is inactive in the electrolytic reaction at the cathode, but it is preferable to use a normal mineral acid in terms of cost, and particularly the material and the yield. From this point of view, sulfuric acid is a preferred mineral acid, and an aqueous 5-30 wt% sulfuric acid solution is usually used.

The concentration of m-hydroxybenzoic acid in sulfuric acid aqueous solution is usually 5
~ 20% by weight.

The cleaning agent used in the present invention is a solvent capable of dissolving m-HBA and a tar-like decomposition product of the product, and has an adverse effect on the electrodes constituting the electrolytic cell and the ion exchange membrane used as the diaphragm. There is no need of. That is, lower alcohols such as methanol, ethanol, isopropanol and t-butanol are preferable.

The electrolyzer may be washed at any time, and may be washed daily for each batch, but once for every 2 to 7 batches, preferably once for every 3 to 6 batches in order to improve the efficiency of the reaction. Is most efficient. Further, the amount of solvent to be washed may be an appropriate amount capable of removing decomposed products.

In the method of the present invention, the electrolytic reduction reaction is carried out in the temperature range of 20 to 70 ° C. Among the electrodes used for electrolysis, the cathode material having a high hydrogen overvoltage, specifically zinc, lead, cadmium, or mercury is used. The opposite anode is not particularly limited as long as it is an ordinary electrode material.

It is preferable to separate the anode chamber and the cathode chamber by a cation exchange membrane. As the material of the diaphragm, asbestos, ceramics, sintered glass or the like can be used.

In the electrolytic reduction of the present invention, the current density is preferably 5 to
It is 30 A / dm ² . Theoretically 4-electron reduction, 4Fr / mol
e Although it is an energization amount, since the current efficiency is 50 to 70%, it is necessary to pass an electricity amount of 5 to 8 Fr / mole to complete the reaction.

Action and effect The method of the present invention, the electrolytic reduction reaction of m-HBA in an acidic aqueous solution is continuously carried out in a batch manner, when producing m-HBOH,
By cleaning the inside of the electrolytic cell with lower alcohols every few batches, accumulation of tar-like decomposition products on the electrode surface can be prevented, and the electrolytic reduction reaction can be operated stably for a long period of time, which is of great industrial value. It is an invention.

Examples Hereinafter, the method of the present invention will be described in detail with reference to Examples.

Example 1 Both electrode chambers had a capacity of 300 ml, and selemion C was used as a diaphragm.
Using an H type electrolytic cell isolated by MY (a cation exchange membrane under the trade name of Asahi Glass Co., Ltd.), 200 ml of a 10% sulfuric acid aqueous solution is charged in each of the electrode chambers. A 50 cm ₂ lead plate was used as the cathode, and a 50 cm ² platinum plate was used as the anode. While keeping the electrolysis cell at 60 ° C, while applying a constant DC current of 6 A, 25 g of m-HBA was added to the catholyte at a rate of 6 g / hour using a micro feeder, and the entire amount of m-HBA was added in 4.2 hours. did. After this, further electrolysis
Continued for 0.8 hours (6.2Fr / mol), after the electrolysis was completed, the catholyte was extracted, and then 200 ml of 10% sulfuric acid aqueous solution was charged again,
Subsequently, the reaction of the second batch was carried out in the same manner as the first batch. The extracted catholyte was analyzed by liquid chromatography (HL
Analysis was performed in C).

When the reaction was completed after the fifth batch, 200 ml of methanol was charged into the cathode tank and stirred at room temperature for 1 hour. Methanol was removed and 10% aqueous sulfuric acid was added again to continue the experiment. Methanol washing was performed every 5 batches, and a total of 20 batches of reaction were continued. Current efficiency, m-
No significant decrease in HBOH yield was observed (see Table 1), the average current efficiency of 20 batches was 61.9%, and the average m-HBOH yield was 90.4%.

Example 2 The same experiment as in Example 1 was carried out continuously for 15 batches except that ethanol was used instead of methanol as the cleaning liquid. No significant decrease in current efficiency and m-HBOH yield was observed,
15 batch average current efficiency 61.4%, average m-HBOH yield 90.9%
Met.

Comparative Example Twelve batches of the same experiment as in Example 1 were conducted except that the washing with the washing liquid was not performed (see Table 2). The current efficiency gradually decreases, and it is 12% in the 12th batch.
Thus, the m-HBOH yield was 18%.

EFFECTS OF THE INVENTION As is clear from the results of Examples and Comparative Examples, in the production of m-HBOH by electrolytic reduction of m-HBA, cleaning was performed every several batches as compared with the method of Comparative Example in which alcohol cleaning in the electrolytic cell was not performed. In the case of carrying out, the current efficiency and the m-HBOH yield are hardly decreased even by repeating the reaction.

That is, when the reaction is continued without cleaning the electrolytic cell, the current efficiency is lowered, and the industrial electrolytic reduction process of m-HBA cannot be realized. However, by inserting a washing process in the middle of each batch, the electrolysis reaction became stable for a long period of time.

Claims (2)

[Claims] 1. In a reaction for electrolytically reducing m-hydroxybenzoic acid in an acidic aqueous solution to obtain m-hydroxybenzyl alcohol, the inside of the electrolytic cell is washed with an alcohol solvent after completion of the electrolytic reaction. -Hydroxybenzyl alcohol production method. 2. An alcohol-based solvent is C _n H _{2n + 1} OH (n is 1
The method according to claim 1, which is an alcohol represented by the formula (1) to (5).