JPS63157891A - Production of m-hydroxybenzyl alcohol - Google Patents

Abstract

PURPOSE:To stably, efficiently, and safely produce the title high-purity m- hydroxybenzyl alcohol in high yield for a long period, by electrolytically reducing m-hydroxybenzoic acid in an aq. acidic soln. added with a surfactant and a defoaming agent. CONSTITUTION:m-Hydroxybenzoic acid is electrolytically reduced in the aq. acidic soln. contg. about 5-20wt% m-hydroxybenzoic acid added with a quaternary ammonium salt-based cationic surfactant and a defoaming agent. Organic silicone is used as the defoaming agent, and 1-1,000ppm agent, based on the aq. acidic soln., is preferably added to the soln. By this method, high-purity m-hydroxybenzyl alcohol is stably obtained in high yield for a long period, and the reaction can be safely carried out while controlling frothing even at a high current density.

Description

[Detailed Description of the Invention] The present invention relates to m-hydroxybenzyl alcohol (hereinafter referred to as
The present invention relates to a method for producing m-HBOH (abbreviated as m-HBOH).

m-HBOH is a compound useful in industry or as an intermediate for agricultural chemicals, but at present it has not been commercially supplied by an inexpensive manufacturing method.

As a method for synthesizing m-HBOH, fermentation using m-cresol as a raw material, sodium amalgam, NaBH4, LiAlH using m-hydroxybenzaldehyde as a raw material, etc.
There are reduction and hydrogenation reactions using No. 4, etc., but these have not been put into practical use due to insufficient yields. Further, the hydrogenation reaction is a reaction at high temperature and high pressure, and there are various problems with industrial production methods.

In addition, regarding the method using m-hydroxybenzoic acid (hereinafter abbreviated as m-HBA) as a raw material, sodium amalgam and electrolytic reduction method have been proposed (Bivricht 3
81752 (1905)), but the yield was low (it could not be an industrial method).

The present inventors first studied methods for producing m-HBOH, and found that a method in which m-HBA is electrolytically reduced in an aqueous solution or a water-soluble organic solvent, and a method in which a supporting electrolyte is added to the catholyte. A method for obtaining m-HBOH in high yield has already been discovered (JP-A-60-234987, JP-A-6O-243293).

5 The present inventors further conducted intensive studies on the industrial production method of m-HBOH, electrolytically reduced m-HBA in an acidic aqueous solution, and produced m-HBOH with high yield and high purity. He first proposed a method to obtain HBOH (Japanese Patent Application No. 60-263858, Patent Application No. 60-
272467).

Furthermore, in Japanese Patent Application No. 61-226134, it was proposed that electrolytic reduction reactions could be carried out stably for a long period of time by adding a surfactant to the reaction system.

However, when a surfactant is added to this electrolytic reaction, there is no problem if the electrolytic current density is relatively low, but if it becomes high, even if the current efficiency is the same, water electrolysis, which is a side reaction, will occur. Since the absolute amount of hydrogen generated increases, foaming caused by the surfactant becomes more intense, and there is a risk that the reaction solution will overflow from the electrolytic cell.

Furthermore, in this electrolytic reaction, if the current efficiency is the same, the higher the current density, the shorter the reaction time and the higher the volumetric efficiency.

However, when a surfactant is added, electrolysis can only be performed at a low current density due to foaming. Therefore, in order to carry out this electrolytic reaction efficiently and safely, it is important to prevent foaming caused by the surfactant.

The problem of the present invention is to prevent foaming and to obtain high-purity m-HBOH in a method that stabilizes electrolytic reduction for a long period of time by adding a surfactant to m-HBA in an acidic aqueous solution. An object of the present invention is to provide an improved method for producing m-HBOH, which aims to carry out the reaction efficiently and safely even at current densities.

. In order to solve the above problem, the inventors of the present invention have made extensive studies to solve the above problem, and found that foaming can be prevented by adding a small amount of antifoaming agent to the reaction system.
They discovered that electrolysis can be performed at high current density and completed the present invention.

That is, the present invention is characterized in that when m-hydroxybenzoic acid is electrolytically reduced by adding a surfactant in an acidic aqueous solution, an antifoaming agent is added to the electrolytic solution and the electrolysis is carried out at 20 to 70'C. This is a method for producing m-hydroxybenzyl alcohol.

In the present invention, the acidic aqueous solution is not particularly limited as long as it is an acidic substance that is inert to the electrolytic reaction at the cathode, but from the viewpoint of cost, it is usually desirable to use mineral acids, especially in terms of material quality and yield. From this point of view, sulfuric acid is a preferred mineral acid, and a 5-30% by weight aqueous sulfuric acid solution is usually used.

The concentration of 3-hydroxybenzoic acid in acidic aqueous solution is usually 5
~20% by weight.

The surfactant used in the method of the present invention has the following formula (1) (wherein, R3, R2, R3 and R1 are an alkyl group or an alkylpolyoxyethylene group, which may be the same or different from each other, is a CI or Br atom), and the amount added to the acidic aqueous solution is 0.
．． 001 to 1% by weight.

If the amount added is less than 0.001% by weight, emulsification of the tar-like byproducts will be insufficient and the byproducts will adhere to the electrode surface. Further, even if the amount exceeds 1% by weight, no further improvement in the emulsifying effect is observed.

The antifoaming agent used in the method of the present invention is preferably a silicone antifoaming agent. The amount added is 71% relative to the acidic aqueous solution that is the solvent.
~1000 ppm, preferably 10-2o.

It is in the ppm range. If the amount added is less than 1 ppm, the antifoaming effect will be insufficient. Moreover, even if it exceeds 1000 pp;, no further improvement in the antifoaming effect is observed.

In the method of the present invention, the electrolytic reduction reaction is carried out at a temperature range of 20 to 70"C. Also, among the electrodes used for electrolysis, the cathode material has a high hydrogen overvoltage, specifically zinc, lead, cadmium, mercury, etc. For the anode,
There is no particular limitation as long as it is a normal electrode material.

Preferably, the anode chamber and the cathode chamber are separated by a cation exchange membrane. As the material for the diaphragm, asbestos, ceramics, sintered glass, etc. can be used.

In the electrolytic reduction of the present invention, the current density is preferably 5 to
30A/dm".Theoretically, it is a 4-electron reduction,
The current flow rate is 4 Fr/note, but the current efficiency is 50
~70%, so it takes 5-8 FR to complete the reaction.
/mole of electricity must pass through it.

The method of the present invention involves adding a surfactant to m-HBA in an acidic aqueous solution and performing an electrolytic reduction reaction to produce m-HBOH, by adding an antifoaming agent to the acidic aqueous solution. By doing so, the electrolytic reduction reaction can be carried out safely and efficiently at a high current density while preventing foaming, which is an extremely valuable invention industrially.

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

Example 1 Using an H-type electrolytic cell with a capacity of 300 m1 for both electrode chambers and separated by Selemion CMV (a cation exchange membrane manufactured by Asahi Glass) as a diaphragm, 10% sulfuric acid was added to the electrode chambers. Pour in 200ml of aqueous solution. 50c as cathode
J lead plate and a 50c+fl platinum plate were used as the anode.

Furthermore, distearyldimethylammonium chloride (Kotami 7 Pressure 4P = Kao Soap) is used as a surfactant in the cathode chamber.
0.2g, and 5H200()-Les silicone)0
．． 01g was added.

While keeping the electrolytic cell at 60°C, the IOA (2OA/d
25 g of m-HBA was added to the catholyte at a rate of 10 g/hour using a microfeeder while applying a constant DC current of 2.5 hours, and the entire amount of m-HBA was added in 2.5 hours. After this, Electrolysis was further continued for 0.9 hours (7Fr/m
ol). After the electrolysis was completed, the catholyte was extracted and analyzed by liquid chromatography (HLC). As a result, the residual rate of m-HBA was 0.2%, and the yield of m-HBOH was 95.6% (all based on the m-HBA used). , the current efficiency was 57.0%.

Example 2 In a reactor similar to Example 1, 200 ml of 10% aqueous sulfuric acid solution was charged into both electrode chambers. Furthermore, 0.1 g of benzethonium chloride and 0.02 g of 5H5500 ()-resilicone) were added to the cathode chamber.

15A (30A/d) while maintaining the electrolytic cell at 60"C
While applying a constant DC current of m2), 25 g of m-HBA was added to the catholyte at a rate of 15 g/hour using a microfeeder, and the entire amount of m-HBA was added in 1.7 hours. After this, electrolysis was further continued for 0.6 hours (7Fr/"
ol). After the electrolysis was completed, the catholyte was analyzed using IILc, and the residual m-HBA rate was 0.9%, and the m-HB OH yield was 94.
．． 8%, and the current efficiency was 56.6%.

Comparative Example 1 The same reaction as in Example 2 was carried out except that the antifoaming agent 5H5500 was not added. During the reaction, approximately 10% of the catholyte spilled out of the electrolytic cell due to bubbling.

After the electrolysis, the remaining catholyte was analyzed by HLC, and m
-HBA residual rate 15.2%, m-HBOH yield 71.4
%, and the current efficiency was 48.5%.

As is clear from the results of the Examples and Comparative Examples, m-HBO is produced by electrolytic reduction of m-HBA in the presence of a surfactant.
In the production of H, no foaming occurred and the current efficiency did not decrease when an antifoaming agent was added, compared to the method of the comparative example in which an antifoaming agent was not added to the reaction system. In other words, if an antifoaming agent is not added, the reaction must be carried out at a low current density to suppress foaming, and in order to supply the amount of electricity necessary for the reaction, the reaction time will inevitably become longer and the reaction will be delayed. volumetric efficiency deteriorates. However, the addition of antifoaming agents enabled the reaction to occur at higher current densities, improving efficiency. Furthermore, there is no need to worry about overflow of the reaction solution due to foaming.

Claims (1)

[Claims] 1) A method for obtaining m-hydroxybenzyl alcohol by electrolytically reducing m-hydroxybenzoic acid in an acidic aqueous solution by adding a surfactant, which is characterized by adding an antifoaming agent. Method for producing m-hydroxybenzyl alcohol. 2) Claim 1 in which the antifoaming agent is an organic silicone
Manufacturing method described in section. 3) The amount of antifoaming agent used is 1 to 10% of the acidic aqueous solution.
00 ppm, the manufacturing method according to claim 1.