Low-nitrogen high-purity potassium persulfate and synthesis method thereof

Abstract

The invention relates to the field of potassium persulfate synthesis, in particular to low-nitrogen high-purity potassium persulfate and a synthesis method thereof. According to the synthesis method of the potassium persulfate, heating and heat preservation are carried out in the synthesis process, after the reaction is finished, the potassium persulfate is cooled to a certain temperature, then the potassium persulfate is rapidly placed in a low-temperature environment to be subjected to a low-temperature crystallization technology, potassium persulfate crystals are obtained, and low-nitrogen and high-purity potassium persulfate can be obtained through subsequent cleaning, centrifugal drying. According to the method, separation of nitrogen-containing impurities and potassium persulfate can be effectively promoted by combining heat-preservation stirring with a freezing crystallization technology, the crystallization time is shortened, and the product has higher crystallinity, so that the production efficiency and the product quality are improved.

Description

Technical Field

[0001] The invention relates to the field of potassium persulfate synthesis, and in particular to low-nitrogen high-purity potassium persulfate and a synthesis method thereof. Background Art

[0002] Potassium persulfate, also known as potassium peroxydisulfate, is a colorless or white crystalline powder with no odor. It is soluble in water but insoluble in ethanol. Its aqueous solution is acidic. Its relative density is 2.477. It has strong oxidizing properties.

[0003] Potassium persulfate is generally prepared by double decomposition reaction of ammonium sulfate and potassium sulfate, and then purified by recrystallization. The raw materials of this preparation method are easy to introduce ammonium salt impurities, and the ammonia released by the reaction cannot be fully released, so that the total nitrogen content in potassium persulfate exceeds the 0.05% required by the national standard (GB / T641-2011) of the chemical reagent potassium persulfate (potassium persulfate), and it is difficult to obtain high-content potassium persulfate.

[0004] Ultraviolet spectrophotometry is widely used in the determination of total nitrogen, with the advantages of simple operation, fast speed, and simple equipment. Therefore, alkaline potassium persulfate spectrophotometry is a common method for determining total nitrogen. Controlling the blank value in the total nitrogen determination process is of great significance to improving the accuracy of water quality total nitrogen monitoring data. Therefore, how to obtain potassium persulfate with low total nitrogen content is the key. Summary of the invention

[0005] In order to solve the above problems, the present invention discloses a low-nitrogen high-purity potassium persulfate and a synthesis method thereof, and the prepared finished product has more stable properties, less nitrogen content and higher purity potassium persulfate.

[0006] A method for synthesizing low-nitrogen high-purity potassium persulfate, characterized in that it comprises the following steps:

[0007] S1 Synthesis Filtration: Add ammonium persulfate to a reactor, add deionized water, stir and dissolve, add potassium hydroxide solution to form a mixed solution, heat the mixed solution and keep it warm to obtain a reaction solution; filter the reaction solution while it is hot and collect the filtrate;

[0008] S2 cooling and freezing crystallization: the filtrate obtained in step S1 is placed in a cooling kettle, cooled to 30°C by stirring with cooling water, and then the cooling kettle containing the filtrate is directly cooled to ≤0°C for low temperature crystallization to obtain potassium persulfate crystals;

[0009] S3 crystal washing, centrifugation and drying: deionized water is added to the potassium persulfate crystals obtained in step S2, and repeated washing and centrifugation is performed. The potassium persulfate crystals after centrifugation are placed in a dryer for drying to obtain low-nitrogen and high-purity potassium persulfate.

[0010] Preferably, in the S1 synthesis filtration step, ammonium persulfate is dissolved in deionized water to produce persulfate ions, and potassium hydroxide is dissolved in deionized water to produce potassium ions, wherein the molar ratio of persulfate ions to potassium ions is 1:(2-2.2).

[0011] Preferably, in the S1 synthesis filtration step, the mass fraction of ammonium persulfate is 29.4-35.7%.

[0012] Preferably, in the S1 synthesis filtration step, the temperature at which the mixed solution is heated is 45-50°C.

[0013] Preferably, in the S1 synthesis filtration step, the insulation time is 30 to 60 minutes.

[0014] Preferably, in the S1 synthetic filtration step, a filter element with a pore size of 4 to 6 μm is used for filtration.

[0015] Preferably, in the step S2 of cooling and freezing crystallization, the temperature of the low-temperature crystallization is specifically -10 to -25°C.

[0016] Preferably, in the crystal washing and centrifugal drying step S3, the deionized water washing is repeated 2 to 4 times.

[0017] Preferably, in the step S3 of washing crystals and centrifugally drying, the drying machine adopts reduced pressure drying, the drying temperature is 40-50° C., and the drying time is 2.7-3.2 h.

[0018] A low-nitrogen high-purity potassium persulfate is prepared by any of the above-mentioned synthesis methods of low-nitrogen high-purity potassium persulfate.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for synthesizing low-nitrogen high-purity potassium persulfate, wherein the molar ratio of ammonium persulfate to potassium hydroxide is 1:2, the heating temperature in the reaction process is controlled to rise to 45-50°C, the heating is stopped, and the temperature is kept warm for 30-60 minutes, and then the temperature is lowered to 30°C after the reaction is completed, and then the temperature is quickly lowered to -10--25°C for crystallization. This method promotes the effective separation of nitrogen-containing impurities and target potassium persulfate by combining heat preservation and stirring with freezing crystallization technology, reduces the crystallization time, and makes the product have a higher degree of crystallinity, thereby improving production efficiency and product quality.

[0021] The invention provides a method for synthesizing low-nitrogen high-purity potassium persulfate, which is simple to operate, environmentally friendly and easy to realize industrial production. DETAILED DESCRIPTION

[0022] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0023] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0024] Example 1: A method for synthesizing low-nitrogen high-purity potassium persulfate, comprising the following steps:

[0025] S1 synthetic filtration: 50g of ammonium persulfate raw material is added to the reactor, and deionized water is added and stirred to dissolve, so that the mass fraction of the ammonium persulfate solution is 35.7%; then 49g of a potassium hydroxide solution with a mass fraction of 50% is added and continued to be stirred evenly. At this time, the molar ratio of persulfate ion to potassium ion is 1:2, and then heated to 50°C, the heating is stopped, and the stirring is continued for 40 minutes and then kept warm to obtain a reaction solution; the reaction solution is subjected to secondary filtration using a filter element with a pore size of 4 to 6 μm while hot and the filtrate is collected.

[0026] S2 Cooling and freezing crystallization: The filtrate obtained in step S1 is placed in a kettle, and cooling water is passed through the kettle at a speed of 20 r / min to stir the filtrate to lower its temperature to 30°C, then the stirring is turned off, and the mixture is directly transferred to a -16°C environment for low-temperature crystallization until a large amount of material is precipitated. The crystallization time is 3 hours, and potassium persulfate crystals are obtained.

[0027] S3 crystal washing and centrifugal drying: adding deionized water to the potassium persulfate crystals obtained in step S2 and washing them repeatedly for 2 times, and then putting them into a centrifuge for centrifugation for 20 minutes; putting the centrifuged potassium persulfate crystals into a dryer for drying under reduced pressure at a temperature of 40°C, and drying for 2.7 hours to obtain low-nitrogen high-purity potassium persulfate.

[0028] Example 2: A method for synthesizing low-nitrogen high-purity potassium persulfate, comprising the following steps:

[0029] S1 synthetic filtration: add 50g of ammonium persulfate raw material into a reactor, add deionized water and stir to dissolve, so that the mass fraction of the ammonium persulfate solution is 33.3%; then add 50g of a 50% potassium hydroxide solution and continue to stir evenly. At this time, the molar ratio of persulfate ion to potassium ion is 1:2.03, and then heat to 46°C, stop heating, and continue to keep warm and stir for 30 minutes to obtain a reaction solution; use a filter element with a pore size of 4 to 6μm to perform secondary filtration on the reaction solution while it is hot and collect the filtrate.

[0030] S2 Cooling and freezing crystallization: The filtrate obtained in step S1 is placed in a kettle, and cooling water is passed through the kettle at a speed of 20 r / min to stir the filtrate to lower its temperature to 30°C, then the stirring is turned off, and the mixture is directly transferred to a -10°C environment for low-temperature crystallization until a large amount of material is precipitated. The crystallization time is 5 hours, and potassium persulfate crystals are obtained.

[0031] S3 crystal washing and centrifugal drying: adding deionized water to the potassium persulfate crystals obtained in step S2 and washing them repeatedly for 2 times, and then putting them into a centrifuge for centrifugation for 20 minutes; putting the centrifuged potassium persulfate crystals into a dryer for drying under reduced pressure at a temperature of 42°C, and drying for 2.8 hours to obtain low-nitrogen high-purity potassium persulfate.

[0032] Example 3: A method for synthesizing low-nitrogen high-purity potassium persulfate, comprising the following steps:

[0033] S1 synthetic filtration: 50g of ammonium persulfate raw material is added to the reactor, and deionized water is added and stirred to dissolve, so that the mass fraction of the ammonium persulfate solution is 31.2%; then 51g of a potassium hydroxide solution with a mass fraction of 50% is added and continued to be stirred evenly. At this time, the molar ratio of persulfate ion to potassium ion is 1:2.07, and then heated to 47°C, the heating is stopped, and the stirring is continued for 60 minutes and then kept warm to obtain a reaction solution; the reaction solution is filtered for secondary use with a filter element with a pore size of 4 to 6μm while it is hot and the filtrate is collected.

[0034] S2 Cooling and freezing crystallization: The filtrate obtained in step S1 is placed in a kettle, and cooling water is passed through the kettle at a speed of 20 r / min to stir the filtrate to lower its temperature to 30°C, then the stirring is turned off, and the mixture is directly transferred to a -20°C environment for low-temperature crystallization until a large amount of material is precipitated. The crystallization time is 3 hours, and potassium persulfate crystals are obtained.

[0035] S3 crystal washing and centrifugal drying: adding deionized water to the potassium persulfate crystals obtained in step S2 and washing them repeatedly for 3 times, and then putting them into a centrifuge for centrifugation for 20 minutes; putting the centrifuged potassium persulfate crystals into a dryer for drying under reduced pressure at a temperature of 44°C, and drying for 2.9 hours to obtain low-nitrogen high-purity potassium persulfate.

[0036] Example 4: A method for synthesizing low-nitrogen high-purity potassium persulfate, comprising the following steps:

[0037] S1 synthetic filtration: add 50g of ammonium persulfate raw material into a reactor, add deionized water and stir to dissolve, so that the mass fraction of the ammonium persulfate solution is 29.4%; then add 52g of a 50% potassium hydroxide solution and continue to stir evenly, at this time the molar ratio of persulfate ion to potassium ion is 1:2.11, then heat to 50°C, stop heating and do not keep warm to obtain a reaction solution; use a filter element with a pore size of 4 to 6μm to perform secondary filtration on the reaction solution while it is hot and collect the filtrate.

[0038] S2 Cooling and freezing crystallization: The filtrate obtained in step S1 is placed in a kettle, and cooling water is passed through the kettle at a speed of 20 r / min to stir the filtrate to lower its temperature to 30°C, then the stirring is turned off, and the mixture is directly transferred to a 0°C environment for low-temperature crystallization until a large amount of material is precipitated. The crystallization time is 10 hours, and potassium persulfate crystals are obtained.

[0039] S3 crystal washing and centrifugal drying: the potassium persulfate crystals obtained in step S2 are placed in a centrifuge for centrifugation for 20 minutes; the potassium persulfate crystals after centrifugation are placed in a dryer for drying under reduced pressure at a temperature of 46°C, and low-nitrogen high-purity potassium persulfate is obtained after drying for 3.0 hours.

[0040] Example 5: A method for synthesizing low-nitrogen high-purity potassium persulfate, comprising the following steps:

[0041] S1 synthetic filtration: add 50g of ammonium persulfate raw material into a reactor, add deionized water and stir to dissolve, so that the mass fraction of the ammonium persulfate solution is 29.4%; then add 52g of a 50% potassium hydroxide solution and continue to stir evenly. At this time, the molar ratio of persulfate ion to potassium ion is 1:2.11, and then heat to 48°C, stop heating, and continue to keep warm and stir for 50 minutes to obtain a reaction solution; use a filter element with a pore size of 4 to 6μm to perform secondary filtration on the reaction solution while it is hot and collect the filtrate.

[0042] S2 Cooling and freezing crystallization: The filtrate obtained in step S1 is placed in a kettle, and cooling water is passed through the kettle at a speed of 20 r / min to stir the filtrate to lower its temperature to 30°C, then the stirring is turned off, and the mixture is directly transferred to a -25°C environment for low-temperature crystallization until a large amount of material is precipitated. The crystallization time is 3 hours, and potassium persulfate crystals are obtained.

[0043] S3 crystal washing and centrifugal drying: adding deionized water to the potassium persulfate crystals obtained in step S2 and washing them repeatedly for 4 times, and then putting them into a centrifuge for centrifugation for 20 minutes; putting the centrifuged potassium persulfate crystals into a dryer for drying under reduced pressure at a temperature of 48°C, and drying for 3.1 hours to obtain low-nitrogen high-purity potassium persulfate.

[0044] Example 6: A method for synthesizing low-nitrogen high-purity potassium persulfate, comprising the following steps:

[0045] S1 synthetic filtration: 50g of ammonium persulfate raw material is added to the reactor, and deionized water is added and stirred to dissolve, so that the mass fraction of the ammonium persulfate solution is 26.3%; then 54g of a 50% potassium hydroxide solution is added and continued to be stirred evenly. At this time, the molar ratio of persulfate ion to potassium ion is 1:2.20, and then heated to 45°C, the heating is stopped, and the stirring is continued for 90 minutes and then kept warm to obtain a reaction solution; the reaction solution is subjected to secondary filtration using a filter element with a pore size of 4 to 6 μm while hot and the filtrate is collected.

[0046] S2 Cooling and freezing crystallization: The filtrate obtained in step S1 is placed in a kettle, and cooling water is passed through the kettle at a speed of 20 r / min to stir the filtrate to lower its temperature to 30°C, then the stirring is turned off, and the mixture is directly transferred to a 0°C environment for crystallization until a large amount of material is precipitated. The crystallization time is 10 hours, and potassium persulfate crystals are obtained.

[0047] S3 crystal washing and centrifugal drying: adding deionized water to the potassium persulfate crystals obtained in step S2 and washing them repeatedly for 4 times, and then putting them into a centrifuge for centrifugation for 20 minutes; putting the centrifuged potassium persulfate crystals into a dryer for drying under reduced pressure at a temperature of 50°C, and drying for 3.2 hours to obtain low-nitrogen high-purity potassium persulfate.

[0048] The main parameters examined in the synthesis reaction of potassium persulfate in Examples 1 to 6 are shown in the following table:

[0049]

[0050] Comparative Example 1: A method for synthesizing low-nitrogen high-purity potassium persulfate, comprising the following steps:

[0051] S1 synthetic filtration: add 50g of ammonium persulfate raw material into the reactor, add deionized water and stir to dissolve, so that the mass fraction of the ammonium persulfate solution is 35.7%; then add 49g of potassium hydroxide solution with a mass fraction of 50% and continue to stir evenly. At this time, the molar ratio of persulfate ion to potassium ion is 1:2, and then heat to 30°C, then keep warm and stir for 20 minutes, keep warm, continue to heat to 50°C, keep warm for 20 minutes, and obtain a reaction solution; use a filter element with a pore size of 4 to 6μm to perform secondary filtration on the reaction solution while it is hot and collect the filtrate.

[0052] The reaction conditions and parameters in the S2 cooling and freezing crystallization step and the S3 crystal washing, centrifugal drying step are the same as those in Example 1.

[0053] Comparative Example 2: A method for synthesizing low-nitrogen high-purity potassium persulfate, comprising the following steps:

[0054] S1 synthetic filtration: add 50g of ammonium persulfate raw material into the reactor, add deionized water and stir to dissolve, so that the mass fraction of the ammonium persulfate solution is 35.7%; then add 49g of potassium hydroxide solution with a mass fraction of 50% and continue to stir evenly. At this time, the molar ratio of persulfate ion to potassium ion is 1:2, and then heat to 30°C, then keep warm and stir for 20 minutes, keep warm, continue to heat to 50°C, keep warm for 20 minutes, and obtain a reaction solution; use a filter element with a pore size of 4 to 6μm to perform secondary filtration on the reaction solution while it is hot and collect the filtrate.

[0055] S2 Cooling and freezing crystallization: The filtrate obtained in step S1 is placed in a kettle, and cooling water is passed through the kettle at a speed of 20 r / min to stir the filtrate to lower its temperature to 0°C, and then the stirring is turned off to carry out crystallization until a large amount of material is precipitated. The crystallization time is 12 hours, and potassium persulfate crystals are obtained.

[0056] The reaction conditions and parameters in step S3 of crystal washing, centrifugal drying are the same as those in Example 1.

[0057] The potassium persulfate prepared in Examples 1 to 6 and Comparative Examples 1 to 2 was tested, and the test results are shown in the following table:

[0058] Example Appearance <![CDATA[Purity (K2S2O8)]]> Total nitrogen (N) Yield GB / T 641-2011 Colorless or white crystalline powder ≥99.5％ ≤0.005％ / Example 1 White crystalline powder 99.80％ ＜0.005％ 78％ Example 2 White crystalline powder 99.72％ ＜0.005％ 70％ Example 3 White crystalline powder 99.75％ ＜0.005％ 72％ Example 4 White crystalline powder 99.50％ 0.015％ 48％ Example 5 White crystalline powder 99.80％ ＜0.005％ 75％ Example 6 White crystalline powder 99.52％ ＜0.005％ 43％ Comparative Example 1 White crystalline powder 99.45％ 0.006％ 56％ Comparative Example 2 White crystalline powder 99.00％ 0.012％ 43％

[0059] It can be seen from the test data in the above table that the purity of potassium persulfate prepared in Examples 1, 2, 3 and 5 is greater than 99.7%, the nitrogen content is less than 0.005%, and the yield is above 70%.

[0060] Compared with the potassium persulfate synthesis methods provided in Examples 1, 2, 3 and 5, Example 4 lacks the heat preservation and stirring operation, changes the frozen crystallization into an ice water bath crystallization, and lacks the crystal washing operation, which results in the final potassium persulfate having a lower purity, a longer crystallization time and a low yield, and a high total nitrogen content, which does not meet national standards.

[0061] Compared with the potassium persulfate synthesis methods provided in Examples 1, 2, 3 and 5, Example 6 extends the heat preservation and stirring to 90 minutes and changes the frozen crystallization to ice water bath crystallization, which results in lower purity of the potassium persulfate finally obtained, longer crystallization time and lower yield.

[0062] Compared with the potassium persulfate synthesis methods provided in Examples 1, 2, 3 and 5, Comparative Example 1 is to divide the heating and heat preservation stages into two stages, that is, first heating to 30° C., heat preservation for 20 minutes, and then continue to heat to 50° C., and heat preservation for 20 minutes. The final potassium persulfate product has a purity of less than 99.5%, a high nitrogen content and a very low yield.

[0063] Compared with Comparative Example 1, Comparative Example 2 changes the low-temperature crystallization to ice-water bath crystallization, and the purity and yield of the obtained product are further reduced, and the nitrogen content is further increased.

[0064] In summary, the synthesis method of a low-nitrogen high-purity potassium persulfate provided by the present invention controls the insulation time in the S1 synthesis filtration step to be 30 to 60 minutes; controls the crystallization temperature in the S3 cooling and freezing crystallization step to be -10 to -25°C; all raw materials can directly participate in the reaction, with high utilization rate, avoiding certain raw material losses due to the separation and purification of intermediate products; the mass fraction of ammonium persulfate solution ranges from 29.4% to 35.7%, and when the mass fraction of ammonium persulfate solution is too high, the reaction is easy to wrap impurities; when the mass fraction of ammonium persulfate solution is too low, the yield of potassium persulfate will be reduced. Among them, the experimental conditions and reaction parameters of Example 1 are optimal, and the purity and yield of the obtained potassium persulfate are high and the nitrogen content is low.

[0065] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for synthesizing low-nitrogen high-purity potassium persulfate, characterized in that: The following steps are involved: S1 Synthesis Filtration: Add ammonium persulfate to a reaction kettle, add deionized water, stir and dissolve, add potassium hydroxide solution to form a mixed solution, heat the mixed solution and keep it warm to obtain a reaction solution; filter the reaction solution while it is hot and collect the filtrate; S2 cooling and freezing crystallization: the filtrate obtained in step S1 is placed in a cooling kettle, cooled to 30°C by stirring with cooling water, and then the cooling kettle containing the filtrate is directly cooled to ≤0°C for low temperature crystallization to obtain potassium persulfate crystals; S3 crystal washing, centrifugation and drying: adding deionized water to the potassium persulfate crystals obtained in step S2, washing and centrifuging repeatedly, placing the potassium persulfate crystals after centrifugation in a dryer for drying, and obtaining low-nitrogen high-purity potassium persulfate.

2. The method for synthesizing low-nitrogen high-purity potassium persulfate according to claim 1, characterized in that: In the S1 synthesis filtration step, ammonium persulfate is dissolved in deionized water to produce persulfate ions, and potassium hydroxide is dissolved in deionized water to produce potassium ions, wherein the molar ratio of persulfate ions to potassium ions is 1:(2-2.2).

3. The method for synthesizing low-nitrogen high-purity potassium persulfate according to claim 1, characterized in that: In the S1 synthesis filtration step, the mass fraction of ammonium persulfate is 29.4-35.7%.

4. The method for synthesizing low-nitrogen high-purity potassium persulfate according to claim 1, characterized in that: In the S1 synthesis filtration step, the mixed solution is heated to a temperature of 45 to 50°C.

5. The method for synthesizing low-nitrogen high-purity potassium persulfate according to claim 1, characterized in that: In the S1 synthesis filtration step, the insulation time is 30 to 60 minutes.

6. The method for synthesizing low-nitrogen high-purity potassium persulfate according to claim 1, characterized in that: In the S1 synthesis filtration step, a filter element with a pore size of 4 to 6 μm is used for filtration.

7. The method for synthesizing low-nitrogen high-purity potassium persulfate according to claim 1, characterized in that: In the step S2 of cooling and freezing crystallization, the temperature of the low-temperature crystallization is specifically -10 to -25°C.

8. The method for synthesizing low-nitrogen high-purity potassium persulfate according to claim 1, characterized in that: In the step S3 of washing crystals and centrifugation drying, washing with deionized water is repeated 2 to 4 times.

9. The method for synthesizing low-nitrogen high-purity potassium persulfate according to claim 1, characterized in that: In the S3 crystal washing centrifugal drying step, the dryer adopts reduced pressure drying, the drying temperature is 40-50°C, and the drying time is 2.7-3.2h.

10. Potassium persulfate produced by the method for synthesizing low-nitrogen high-purity potassium persulfate according to any one of claims 1 to 9.

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