JPS6023652B2 - Hydroquinone production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydroquinone by hydrolyzing a hydrohalide salt of para-aminophenol.

It has been known to produce hydroquinone by hydrolyzing para-aminophenol using acidic ammonium sulfate. However, in the conventionally known method using acidic ammonium sulfate, a high molar ratio of 2 mol of acidic ammonium sulfate to 1 mol of para-aminophenol is required for the reaction to proceed, which significantly increases the cost of reaction equipment. , and the yield of hydroquinone was about 70% at most.

(U.S. Patent No. 3,862,247) As a result of searching for various methods for producing hydroquinone by hydrolyzing para-aminophenol, the present inventors found that the reaction between para-aminophenol and hydrohalic acid is different from the conventional reaction using acidic ammonium sulfate. The present inventors have found that the process can proceed easily even when the molar ratio of hydrogen halide to para-aminophenol is as low as 1, and that hydroquinone can be produced in an extremely good yield, and the method of the present invention has been developed.

That is, in the method of the present invention, hydrohalic acid and para-aminophenol are mixed in a 1.5 to 1.5 molar ratio of hydrogen halide to para-aminophenol in a range of 1.0 to 1.5.
This is a method in which the reaction is carried out at a temperature of 0°C or higher; for example, the molar ratio of hydrogen halide to para-aminophenol is 1.
The yield of hydroquinone based on the para-aminophenol used can easily be 90% or more by reacting with the concentration of para-aminophenol in the reaction solution in the range of 1-5% by weight. I can do it.

Specific examples of hydrohalic acids used in the reaction include:
Examples include hydrochloric acid, hydrobromic acid, and hydroiodic acid. The molar ratio of hydrogen halide and para-aminophenol is 1.0 to 1.5
is within the range of

If the molar ratio of hydrogen halide to para-aminophenol is small, the amount of unreacted para-aminophenol in the reaction product solution will increase, making the usual recycling of unreacted substances to the reaction system complicated. On the other hand, if the molar ratio is too large, corrosion of the reactor material increases, resulting in increased formation of tar-like substances and a decrease in the yield of the desired hydroquinone. When the molar ratio of hydrogen halide to para-aminophenol is in the range of 1.0 to 1.5,
In terms of the above-mentioned circulation of unreacted materials and corrosion of the reactor material,
More advantageously, in the production of industrial hydroquinone, molar ratios such as, for example, 1.1 are used. There are no particular limitations on the concentration of para-aminophenol in the reaction solution, but a range of usually 1 to 8% by weight, preferably 1 to 5% by weight is used. If the concentration of para-aminophenol in the reaction solution exceeds 8% by weight, the reaction tube or reactor is likely to be clogged due to the ammonium halide crystals generated, and if it is less than 1% by weight, the reaction will be interrupted. The equipment efficiency is poor and it is not economical. The temperature at which this method is carried out is above 150°C, preferably between 200°C and above.
30,000, and if the temperature is lower than 150,000, the reaction rate is too slow to be practical.

The amount of water used in this reaction is para-aminophenol 1
Generally, 1 mol or more is required to obtain hydroquinone in good yield per mol, but 4 mol or more is preferably used.

The reaction time varies depending on the temperature at which the reaction is carried out, but is usually about several minutes to 8 hours.

The reaction pressure may be the pressure necessary to maintain the liquid phase, but an inert gas such as nitrogen, helium, argon, hydrogen,
Pressurization may be performed using carbon monoxide or the like.

This method can be carried out either batchwise or continuously. In this method, the yield of hydroquinone is significantly affected by the material of the reactor.

If a material that is corroded by the reaction solution is used, tar formation will be significantly increased and the yield of hydroquinone will be low. It is convenient to use a material that is substantially free from corrosion as the material used in this reaction. Examples of such materials include molybdenum, tungsten, gold, platinum, titanium, zirconium, tantalum, or alloys containing them, Hastelloy (trade name) such as Hastelloy A, Hastelloy B, Hastelloy C, Hastelloy D, Hastelloy F, etc. Alloy or Teflon (
Product names), impermeable graphite, glass, enamel, ceramic, acid-resistant stoneware, brewing-resistant, etc. There are no particular limitations on the method for separating hydroquinone from the aqueous solution containing hydroquinone after the reaction, but a commonly used solvent extraction method can be applied as is.

For example, hydroquinone in an aqueous solution is extracted with ethers such as ethyl ether and isopropyl ether, ketones such as methyl ethyl ketone and methyl isobutylkene, and alcohols such as butyl alcohol and amyl alcohol.
Next, after separating the organic layer and the aqueous layer, hydroquinone can be obtained by distilling the organic layer. On the other hand, the aqueous layer can be circulated to the hydrolysis reaction after distilling off the dissolved extraction solvent. Example 1 0.025 mol of para-aminophenol and 0.0 mol of hydrogen chloride were placed in a Hastelloy B autoclave with an internal volume of 300'.
25 mol and 100 mol of water were charged and reacted at 250 qo for 6 hours.

Thereafter, the autoclave was cooled to room temperature, the contents were taken out, hydroquinone was extracted with ether, a portion of the ether was distilled off, and the autoclave was analyzed by gas chromatography to obtain the following results.

Yield of hydroquinone: 90.1% Example 2 Add 0 para-aminophenol to the autoclave described above.
．． 0.025 mol of hydrogen bromide, 0.025 mol of hydrogen bromide, and 100 mol of water were charged and reacted at 25 mol for 6 hours.

Claims (1)

[Scope of Claims] 1. Hydrohalic acid and para-aminophenol are mixed at a molar ratio of hydrogen halide to para-aminophenol of 1.
．． A method for producing hydroquinone, characterized in that the amount is in the range of 0 to 1.5 mol, and the reaction is carried out at a temperature of 150°C or higher. 2. The method according to claim 1, wherein the reaction temperature is in the range of 200 to 300°C.