JPH0512282B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a method for producing potassium persulfate by reacting ammonium persulfate with potassium hydroxide. The present invention relates to a method for producing solid potassium persulfate. (Prior art and its problems) In the production of potassium persulfate, potassium persulfate is Decomposes in the presence of dissolved ammonia or heavy metal ions, producing potassium sulfate. There is a problem in that potassium persulfate products are contaminated by this potassium sulfate, resulting in a decrease in purity. In order to solve the above problems, we reduced the decomposition rate of persulfates in a method for producing persulfates by reacting ammonium persulfate with hydroxides of alkali metals or alkaline earth metals. Various proposals have been made regarding methods for producing highly pure persulfates by suppressing the production of sulfates. In Japanese Patent No. 1022912, ammonium produced in the reaction of ammonium persulfate with an alkali metal or alkaline earth metal hydroxide and a part of the water present in the system are evaporated in the same system, and then A method has been proposed in which an aqueous solution or slurry of a persulfate in which the ammonia concentration of the reaction product liquid is reduced as much as possible is concentrated under reduced pressure in a system different from the system in which the reaction concentration was performed to crystallize the persulfate. Furthermore, in JP-A-51-122694, ammonia produced by the reaction between ammonium persulfate and sodium hydroxide or potassium hydroxide is treated with a countercurrent gas.
A method has been proposed in which ammonia is removed using a stripper and the ammonia concentration in the reaction solution is kept below 0.5% by weight. However, although these methods reduce the decomposition rate of persulfate due to the decrease in ammonia concentration,
The decomposition of persulfate due to other factors cannot be prevented, so the sulfate in the recycled mother liquor will gradually accumulate and eventually precipitate together with the persulfate, reducing the purity of the product. . Furthermore, in JP-A-58-161907, as a method for removing sodium sulfate produced by the decomposition of sodium persulfate, a part of the mother liquor is diluted and cooled to precipitate as sodium sulfate decahydrate, and this is decomposed and removed. has been proposed, but when this method is adopted for producing potassium persulfate, there is a drawback that potassium persulfate alone or together with potassium persulfate precipitates. In conventional technology, in order to prevent potassium sulfate from being mixed into potassium persulfate products, a part of the reaction mother liquor is discarded, diluted with water and recycled, or the concentration reaches such a level that potassium sulfate precipitates. A method is adopted in which the entire amount of mother liquor is discarded immediately before treatment.
However, this is a very disadvantageous method in terms of economy. (Means for Solving the Problem) As a result of intensive research into a method for producing high-purity potassium persulfate while minimizing loss of mother liquor, the present inventors found that ammonium persulfate and potassium hydroxide After separating the potassium persulfate obtained by the reaction, we have discovered a method in which potassium hydroxide, which is used as a raw material, is added to the separated mother liquor in advance to precipitate potassium sulfate from the mother liquor and remove it, and we have developed the present invention. It came to this. That is, the present invention provides a method for producing potassium persulfate by reacting ammonium persulfate and potassium hydroxide, in which at least a part of the potassium hydroxide used as a raw material is converted into at least a part of the mother liquor after separation of the potassium persulfate crystals produced by the reaction. This is a method for producing high-purity potassium persulfate with a low potassium sulfate content, which is characterized by precipitating and removing potassium sulfate produced by decomposition of potassium persulfate, and recycling the mother liquor. Potassium persulfate products manufactured using conventional methods contain more than 0.5% by weight of potassium sulfate, but by adopting the method of the present invention, the content of potassium sulfate can be reduced to 0.1% by weight or less. It is possible to reduce More specifically, the method of the present invention is a vacuum evaporation method in which ammonium persulfate and potassium hydroxide are reacted in an aqueous solution and the resulting ammonia is evaporated and concentrated under vacuum, or concentrated using a large amount of air under normal pressure. After removing the precipitated potassium persulfate using a stripper method, etc., the precipitated potassium persulfate is separated using a centrifuge, etc., and then potassium hydroxide is added to part or all of the crystallized mother liquor to crystallize and remove the potassium sulfate in the mother liquor. This is a method in which ammonium persulfate is dissolved in the treated mother liquor and reused after the reaction. Regarding the amount of mother liquor to be treated in the method of the present invention, if the amount of potassium persulfate decomposed during the manufacturing process is large, it is desirable to treat the entire amount of mother liquor, but if the amount of decomposition is small, it is preferable to treat some of the mother liquor. It is also possible to treat the mother liquor, and after treatment, to recycle it together with the untreated mother liquor. The addition of potassium hydroxide to the mother liquor after crystal separation ranges from 10% to 60% by weight, preferably 40% by weight.
Potassium hydroxide with a concentration of 55% by weight is added to a part or all of the amount used as a raw material. The temperature for adding potassium hydroxide, precipitating potassium sulfate, and separating the formed crystals is 5°C to 60°C, preferably 15°C to 30°C. Examples will be given below to explain in more detail,
The present invention is not limited in any way by this example. (Example) 10 g of a 50% by weight aqueous potassium hydroxide solution was added to 100 g of a mother liquor having a composition of 2.3% by weight of potassium persulfate and 7.5% by weight of potassium sulfate, and the mixture was kept at 25° C. to precipitate potassium sulfate. After separating the precipitated potassium sulfate crystals, the resulting mother liquor was charged into a reaction tank, and 86.5 g of ammonium persulfate was dissolved in 770 g of the mother liquor having the above composition without any potassium sulfate removal operation, and 76 g of 50% potassium hydroxide was added. It was also supplied to the reaction tank. At this time, the reaction tank was at 25℃ and 18mmHg.
The mixture was held for 30 minutes to remove ammonia produced by the reaction and evaporate 13.6 g of water. The slurry of potassium persulfate thus produced was fed to a centrifugal separator to separate the crystals from the mother liquor, and then the mother liquor was used in the reaction by repeating the same operation as above. The purity of the obtained potassium persulfate crystals was as shown in Table 1. (Comparative Example) A reaction was carried out by repeatedly using the potassium sulfate as it was without performing the removal operation shown in the example.
The purity of the obtained potassium persulfate crystals was as shown in Table 1. 【table】

Claims (1)

[Claims] 1. In a method for producing potassium persulfate by reacting ammonium persulfate and potassium hydroxide,
At least a portion of the potassium hydroxide used as a raw material is added to at least a portion of the mother liquor after separating the potassium persulfate crystals produced by the reaction, and the potassium sulfate produced by decomposition of the potassium persulfate is precipitated and removed, and the mother liquor is recycled. A method for producing high-purity potassium persulfate with a low content of potassium sulfate, which is characterized by recycling.