Preparation method of potassium nitrate and potassium nitrate
Through the three-stage heating process and the method of controlling the addition rate of nitric acid solution, the yield and purity of potassium nitrate is improved, and the problem of low purity and yield of potassium nitrate preparation in the prior art is solved, thereby achieving efficient and environmentally friendly potassium nitrate preparation.
Patent Information
- Application Number
- CN202411299243.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-18
- Publication Date
- 2025-01-07
AI Technical Summary
The existing potassium nitrate preparation methods have problems of low purity and yield and high cost, which are difficult to meet market demand.
The three-stage heating process and the rate of addition of nitric acid solution are used to adjust the heating rate and insulation time of the reaction solution, and the freedom of ion activity is increased by gradually increasing the temperature and cooling to form stable nitrates, thereby increasing the yield of potassium nitrate and purity.
The yield and purity of potassium nitrate has been significantly improved, with a yield of more than 99.0%, a purity of more than 99.80%, and a short process route, no three waste emissions, and low energy consumption, meeting market demand and environmental protection requirements.
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Abstract
Description
Technical Field
[0001] The present application relates to the field of chemical manufacturing technology, and in particular to a method for preparing potassium nitrate and potassium nitrate. Background Art
[0002] Potassium nitrate is an important inorganic salt, presenting as colorless, transparent orthorhombic crystals, rhombic crystals or white powder. It has the properties of high solubility and strong oxidation. It has been widely used in agriculture, industry, aquaculture and other fields.
[0003] At present, the preparation methods of potassium nitrate mainly include double decomposition method and ion exchange method; for example, relevant literature reports a method for preparing potassium nitrate by reacting ammonium nitrate, potassium chloride and magnesium oxide, but in the production process of this method, magnesium chloride hexahydrate equal to potassium nitrate will be mixed in the mother liquor and difficult to remove, resulting in low purity of potassium nitrate after freezing and crystallization; and the above method will also cause at least 10% of potassium nitrate to dissolve in the magnesium chloride solution and be difficult to recover, making the yield of potassium nitrate less than 90%; there is also a related technology reporting a method for preparing potassium nitrate by ion exchange method, but this ion exchange method has the disadvantages of high equipment cost, low yield of potassium nitrate as a finished product, and generation of tail waste resin, so it is difficult to promote on a large scale.
[0004] Therefore, in order to reduce the production cost of potassium nitrate, improve the yield and purity of potassium nitrate, and thus meet the growing market demand, it is particularly important to explore an efficient method for preparing potassium nitrate. Summary of the invention
[0005] In order to overcome the shortcomings of the existing preparation methods of potassium nitrate, such as low purity and yield, and high cost, the present application provides potassium nitrate and a preparation method thereof.
[0006] In a first aspect, the present application provides a method for preparing potassium nitrate, using the following technical solution: A method for preparing potassium nitrate comprises the following steps: (1) firstly, adding potassium chloride solution into a reaction kettle and heating it to 45-50° C.; then, slowly adding nitric acid solution into the reaction kettle at a rate of 0.3-1 mL / s, and then adding water to obtain a reaction solution; (2) The reaction solution is heated according to the following procedure: The first stage: heating at a rate of 1-2℃ / min. When the temperature reaches 60-65℃, stop heating and keep warm for 30-40min. The second stage: heating at a heating rate of 0.1-0.2℃ / min. When the temperature reaches 80-90℃, stop heating and keep warm for 30-40min. The third stage: heating at a heating rate of 1.5-2℃ / min. When the temperature reaches 100-105℃, keep warm for 10-20min. (3) The reaction solution is cooled, neutralized, and post-treated to obtain potassium nitrate.
[0007] The present application provides a method for preparing potassium nitrate. Compared with the related art, the preparation method can significantly improve the yield and purity of the obtained potassium nitrate by controlling the addition rate of nitric acid and adjusting the heating rate and the holding time of the reaction solution to the above range. The yield of potassium nitrate can reach more than 99.0%, and the purity can reach more than 99.80%. In addition, the preparation method of potassium nitrate provided by the present application also has the advantages of short process route, no three wastes discharge, low energy consumption, etc., which can meet market demand and environmental protection requirements.
[0008] The heating step of the present application adopts a three-stage heating process, which can, on the one hand, avoid danger caused by excessively violent reactions; on the other hand, it can continuously provide a stable thermal environment for the system by gradually increasing the temperature, thereby increasing the distance between each ion and the freedom of ion movement, allowing more potassium ions to effectively collide with nitrate ions, thereby quickly and fully forming stable nitrates.
[0009] In some embodiments, the heating rate of the first stage may be 1-1.5° C. / min or 1.5-2° C. / min.
[0010] In a specific embodiment, the heating rate of the first stage may also be 1°C / min, 1.5°C / min or 2°C / min.
[0011] In a specific embodiment, the temperature after the first stage of heating can also be 60°C or 65°C.
[0012] In some embodiments, the insulation time after the first stage of heating can be 30-35 min or 35-40 min. In a specific embodiment, the insulation time after the first stage of heating can also be 30 min, 35 min or 40 min.
[0013] In some embodiments, the heating rate of the second stage may be 0.1-0.15° C. / min or 0.15-0.2° C. / min.
[0014] In a specific embodiment, the heating rate of the second stage may also be 0.1°C / min, 0.15°C / min or 0.2°C / min.
[0015] In some embodiments, the temperature after the second stage of heating can be 80-85°C or 85-90°C.
[0016] In a specific embodiment, the temperature after the second stage of heating can also be 80°C, 85°C or 90°C.
[0017] In some embodiments, the insulation time after the second stage of heating can be 30-35 min or 35-40 min. In a specific embodiment, the insulation time after the second stage of heating can also be 30 min, 35 min or 40 min.
[0018] In a specific embodiment, the heating rate of the third stage can be 1.5°C / min or 2°C / min.
[0019] In a specific embodiment, the temperature after the third stage of heating can be 105°C.
[0020] In some embodiments, the insulation time after the third stage of heating can be 10-15 min or 15-20 min. In a specific embodiment, the insulation time after the third stage of heating can also be 10 min, 15 min or 20 min.
[0021] Optionally, the addition rate of the nitric acid solution is 0.5-0.8 mL / s.
[0022] In some embodiments, the addition rate of the nitric acid solution is 0.3-0.5 mL / s, 0.3-0.8 mL / s, 0.3-1 mL / s, 0.5-0.8 mL / s, 0.5-1 mL / s or 0.8-1 mL / s.
[0023] In a specific embodiment, the addition rate of the nitric acid solution can also be 0.3 mL / s, 0.5 mL / s, 0.8 mL / s or 1 mL / s.
[0024] Optionally, in step (1), the weight ratio of potassium chloride to nitric acid is 1:(0.8-1), and the amount of water added is 4-6 times the total weight of potassium chloride and nitric acid.
[0025] In a specific embodiment, the weight ratio of potassium chloride to nitric acid is 1:0.81.
[0026] In a specific embodiment, the amount of water added is 5 times the total weight of potassium chloride and nitric acid.
[0027] Optionally, the concentration of the potassium chloride solution is 20-25wt%, and the concentration of the nitric acid solution is 56-64wt%.
[0028] In a specific embodiment, the concentration of the potassium chloride solution is 22 wt %, and the concentration of the nitric acid solution is 60 wt %.
[0029] Optionally, the cooling rate is 2-4°C / min.
[0030] Optionally, the temperature after cooling is 22-30°C.
[0031] In the present application, the inventors found that the cooling rate and the temperature after cooling in the preparation method of potassium nitrate have a significant influence on the yield and purity of potassium nitrate. When the cooling rate is too fast, the temperature after cooling is too high or too low, the yield and purity of the obtained potassium nitrate are low. Therefore, the present application found through experimental exploration that further controlling the cooling rate within the above range can obtain a higher yield and purity of potassium nitrate, with a yield of more than 99.5% and a purity of more than 99.90%.
[0032] In some embodiments, the cooling rate may be 2-3°C / min, 2-4°C / min, 2-6°C / min, 3-4°C / min, 3-6°C / min, or 4-6°C / min.
[0033] In a specific embodiment, the cooling rate can also be 2°C / min, 3°C / min, 4°C / min, or 6°C / min.
[0034] In some embodiments, the temperature after cooling can be 15-22°C, 15-30°C, 15-35°C, 22-30°C, 22-35°C or 30-35°C.
[0035] In a specific embodiment, the temperature after cooling can also be 15°C, 22°C, 30°C or 35°C.
[0036] Optionally, the specific steps of the neutralization are: centrifugally filtering the cooled reaction solution, adding the obtained material into a neutralization kettle pre-placed with a saturated potassium nitrate solution, and then adding potassium hydroxide for neutralization, so that the pH of the material is 6.8-7.
[0037] Optionally, the weight of the saturated potassium nitrate solution is 35-55% of the weight of the potassium nitrate crystals, and the temperature of the saturated potassium nitrate solution is 22-30°C.
[0038] In the present application, potassium nitrate is prepared in an acid-resistant reactor capable of providing heating and stirring. The lid of the reactor is provided with a nozzle for discharging HCl gas, and the nozzle is connected to an acid-resistant pipeline leading to a hydrochloric acid absorption device.
[0039] In a second aspect, the present application provides potassium nitrate obtained by a method for preparing potassium nitrate, wherein the purity of the potassium nitrate is ≥99.80%.
[0040] In summary, this application has the following beneficial effects: 1. The present application provides a method for preparing potassium nitrate. The preparation method adopts a three-stage heating process and adjusts the addition rate of a nitric acid solution, so that the yield and purity of potassium nitrate can be significantly improved. The yield of the prepared potassium nitrate can reach more than 99.0%, and the purity can reach more than 99.80%; and the addition rate of the nitric acid solution is further controlled within the range of 0.5-0.8 mL / s, so that the yield and purity of the obtained potassium nitrate are higher, the yield can reach more than 99.5%, and the purity can reach more than 99.90%.
[0041] 2. The present application further controls the cooling rate of the cooling step to 2-4°C / min, and the temperature after cooling is controlled within the range of 22-30°C, which can increase the yield and purity of potassium nitrate, with a yield of ≥99.5% and a purity of potassium nitrate of ≥99.90%.
[0042] 3. The preparation method of potassium nitrate provided in this application also has the advantages of short process route, high production efficiency, no other side reactions, no three wastes discharge, etc., and can meet market demand and environmental protection requirements. DETAILED DESCRIPTION
[0043] The present application provides a method for preparing potassium nitrate, comprising the following steps: (1) adding 20-25 wt% potassium chloride solution to a reaction kettle and heating it to 45-50° C.; then slowly adding 56-64 wt% nitric acid solution to the reaction kettle at a rate of 0.3-1 mL / s and stirring evenly; then adding water in an amount of 4-6 times the total weight of potassium chloride and nitric acid, heating the reaction; wherein the weight ratio of potassium chloride to nitric acid is 1:(0.8-1).
[0044] (2) Slowly heat the reactor through a jacket or coil. The temperature during the heating process is controlled as follows: The first stage: heating at a rate of 1-2℃ / min. When the temperature reaches 60-65℃, stop heating and keep warm for 30-40min. The second stage: heating at a heating rate of 0.1-0.2℃ / min. When the temperature reaches 80-90℃, stop heating and keep warm for 30-40min. The third stage: heating at a heating rate of 1-1.5°C / min. When the temperature reaches 100-105°C, keep it warm for 10-20 minutes.
[0045] (3) After the temperature is raised, clean water at room temperature equivalent to 35-55% of the volume of the material is slowly and evenly added to the reactor; then the reactor is gradually cooled down, and stirring is continued during the cooling process. The cooling rate is controlled at 2-4°C / min until the temperature drops to 22-30°C, potassium nitrate crystals are precipitated, and a reaction solution is obtained.
[0046] (4) The reaction solution is centrifuged and filtered using an acid-resistant centrifuge, and the obtained potassium nitrate crystals are added to a neutralization kettle pre-placed with a saturated potassium nitrate solution, and potassium hydroxide is added for neutralization, so that the pH of the material is 6.8-7. The weight of the saturated potassium nitrate solution is 35-55% of the weight of the potassium nitrate crystals, and the temperature is 22-30°C.
[0047] (5) The neutralized material is centrifuged, washed, and fluidized bed dried to obtain potassium nitrate.
[0048] In the above preparation method, the mother liquor obtained by two centrifugations can be collected and recycled in subsequent production to dissolve potassium chloride; the generated HCl gas is treated by a hydrochloric acid absorption process (absorption with water) to obtain hydrochloric acid, which is used for by-product sales.
[0049] The raw materials, reagents, solvents, etc. used in this application can be obtained commercially.
[0050] The present application is further described in detail below in conjunction with embodiments and performance testing experiments.
[0051] Examples 1-15 Examples 1-15 each provide a method for preparing potassium nitrate.
[0052] The preparation method of the above-mentioned potassium nitrate comprises the following steps: (1) 11 g of potassium chloride is dissolved in 50 g of water to obtain a 22 wt% potassium chloride solution; 14.68 g of a 60 wt% nitric acid solution is taken; the 22 wt% potassium chloride solution is added to a reactor and the temperature is raised to 50° C.; then the 60 wt% nitric acid solution is slowly added to the reactor at a rate of 0.5 mL / s and stirred evenly; then water is added in an amount of 5 times the total weight of potassium chloride and nitric acid, and the temperature is raised to react; wherein the weight ratio of potassium chloride to nitric acid is 1:0.81.
[0053] (2) The reactor is slowly heated in three stages through a jacket or coil, and the rate, temperature, and time control during the three-stage heating process are shown in Table 1. (The heating rates of the three stages are respectively represented by V1, V2, and V3; the temperatures after the three-stage heating are respectively represented by T1, T2, and T3; the holding times after the three-stage heating are respectively represented by t1, t2, and t3).
[0054] (3) After the temperature is raised, clean water at room temperature equivalent to 40% of the volume of the material is slowly and evenly added to the reactor; then the reactor is gradually cooled down, and stirring is continued during the cooling process. The cooling rate is controlled at 3°C / min until the temperature drops to 25°C, potassium nitrate crystals are precipitated, and a reaction solution is obtained.
[0055] (4) The reaction solution is centrifuged and filtered using an acid-resistant centrifuge, and the obtained potassium nitrate crystals are added to a neutralization kettle pre-filled with a saturated potassium nitrate solution, and potassium hydroxide is added for neutralization, so that the pH value of the material is 6.8-7. The weight of the saturated potassium nitrate solution is 40% of the weight of the potassium nitrate crystals, and the temperature is 25°C.
[0056] (5) The neutralized material is centrifuged, washed, and fluidized bed dried to obtain potassium nitrate.
[0057] Comparative Examples 1-7 Comparative Examples 1-7 respectively provide a method for preparing potassium nitrate.
[0058] The difference between the comparative example and Example 2 is that the heating rate V, temperature T and holding time t in the three-stage heating in step (2) are specifically shown in Table 1 below.
[0059] Table 1 Control of various indicators in the three-stage heating process in Examples 1-15 and Comparative Examples 1-7 Example 16-18 Examples 16-18 respectively provide a method for preparing potassium nitrate.
[0060] The difference between the above embodiment and embodiment 2 is that the addition rate of the nitric acid solution is as shown in Table 2 below.
[0061] Comparative Examples 8-9 Comparative Examples 8-9 respectively provide a method for preparing potassium nitrate.
[0062] The difference between the comparative example and Example 2 is that the addition rate of the nitric acid solution is as shown in Table 2 below: Table 2 Addition rate of nitric acid solution in Example 2, Examples 16-18, Comparative Examples 8-9 Examples 19-25 Examples 19-25 each provide a method for preparing potassium nitrate.
[0063] The difference between the above embodiment and embodiment 2 is that the cooling rate and temperature in step (3) are specifically shown in Table 3 below.
[0064] Table 3 Cooling rate and temperature in step (3) of Example 2 and Examples 19-25 Performance test Potassium nitrate was prepared using the potassium nitrate preparation method provided in Examples 1-25 and Comparative Examples 1-9, the mass yield of potassium nitrate was calculated, and the purity of potassium nitrate was tested. The results are shown in Table 4 below.
[0065] The purity of potassium nitrate was detected by acid-base titration; the calculation formula of the mass yield of potassium nitrate was: mass yield of potassium nitrate=actual output of potassium nitrate / theoretical output of potassium nitrate×100%.
[0066] Table 4 Mass yield and purity test results of potassium nitrate obtained in Examples 1-25 and Comparative Examples 1-9 The test results of Examples 1-15 and Comparative Examples 1-7 show that the yield of potassium nitrate obtained in Examples 1-15 of the present application is 99.0-99.8%, and the purity is 99.81-99.94%; while the yield of potassium nitrate obtained in Comparative Examples 1-7 is 84.5-92.3%, and the purity is 97.06-99.02%. Therefore, it is shown that the three-stage heating process adopted in the present application can significantly improve the yield and purity of potassium nitrate, and the yield of the prepared potassium nitrate can reach more than 99.0%, and the purity can reach more than 99.80%.
[0067] The test results of Example 2, Examples 16-18, and Comparative Examples 8-9 show that the yield of potassium nitrate obtained in Example 2 and Examples 16-18 is 99.3-99.8%, and the purity is 99.82-99.94%; while the yield of potassium nitrate obtained in Comparative Examples 8-9 is 88.7-90.4%, and the purity is 97.12-98.35%. Therefore, it is shown that the application adopts the method of gradually adding nitric acid solution and controlling the addition rate within the range of 0.3-1mL / s, which can significantly improve the yield and purity of potassium nitrate. Further comparison shows that the yield of potassium nitrate obtained in Example 2 and Example 17 is 99.6-99.8% (≥99.5%), and the purity is 99.92-99.94% (≥99.90%), which shows that the application further controls the addition rate of nitric acid solution within the range of 0.5-0.8mL / s, and the yield and purity of potassium nitrate obtained are higher.
[0068] The test results of Example 2 and Example 19-25 show that the yield of potassium nitrate obtained in Example 2, Example 19-20, and Example 23-24 is 99.5-99.8% (≥96.0%), and the purity is 99.90-99.94 (≥99.90%); while the yield of potassium nitrate obtained in Example 21-22 and Example 25 is only 99.0-99.3% (<99.5%), and the purity is only 99.83-99.87% (<99.90%). Therefore, it is explained that the present application further controls the cooling rate at 2-4°C / min, and the temperature after cooling is controlled within the range of 22-30°C, which can make the yield and purity of potassium nitrate higher, and the yield can reach more than 99.5%, and the purity can reach more than 99.90%.
[0069] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.
Claims
1. A method for preparing potassium nitrate, characterized in that: The following steps are involved: (1) First, potassium chloride solution is added to the reactor and the temperature is raised to 45-50°C; then nitric acid solution is slowly added to the reactor at a rate of 0.3-1 mL / s, and then water is added to obtain a reaction solution; (2) Heat the reaction solution according to the following procedure: The first stage: heating at a rate of 1-2℃ / min. When the temperature reaches 60-65℃, stop heating and keep warm for 30-40min. The second stage: heating at a rate of 0.1-0.2℃ / min. When the temperature reaches 80-90℃, stop heating and keep warm for 30-40min. The third stage: heating at a heating rate of 1.5-2℃ / min. When the temperature reaches 100-105℃, keep warm for 10-20min. (3) The reaction solution is cooled, neutralized, and post-treated to obtain potassium nitrate.
2. The method for preparing potassium nitrate according to claim 1, wherein The addition rate of the nitric acid solution is 0.5-0.8 mL / s.
3. The method for preparing potassium nitrate according to claim 1, wherein In the step (1), the weight ratio of potassium chloride to nitric acid is 1:(0.8-1), and the amount of water added is 4-6 times the total weight of potassium chloride and nitric acid.
4. The method for preparing potassium nitrate according to claim 1, wherein The concentration of the potassium chloride solution is 20-25wt%, and the concentration of the nitric acid solution is 56-64wt%.
5. The method for preparing potassium nitrate according to claim 1, characterized in that The cooling rate is 2-4°C / min.
6. The method for preparing potassium nitrate according to claim 5, characterized in that: The temperature after cooling is 22-30°C.
7. The method for preparing potassium nitrate according to any one of claims 1 to 6, characterized in that: The specific steps of the neutralization are: centrifugally filtering the reaction solution after cooling, adding the obtained material into a neutralization kettle pre-placed with a saturated potassium nitrate solution, and then adding potassium hydroxide for neutralization, so that the pH of the material is 6.8-7.
8. The method for preparing potassium nitrate according to claim 7, characterized in that: The weight of the saturated potassium nitrate solution is 35-55% of the weight of the potassium nitrate crystals, and the temperature of the saturated potassium nitrate solution is 22-30°C.
9. Potassium nitrate obtained by the method for preparing potassium nitrate according to any one of claims 1 to 8, characterized in that: The purity of the potassium nitrate is ≥99.80%.