Sodium nitrate and preparation process thereof
Through four-stage temperature control reaction and appropriate cooling rate control, the problems of low production efficiency and poor environmental protection in the existing sodium nitrate preparation process were solved, and high-purity and high yield sodium nitrate were obtained to meet market demand and environmental protection requirements.
Patent Information
- Application Number
- CN202411126566.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-16
- Publication Date
- 2024-12-13
AI Technical Summary
The existing sodium nitrate preparation process has problems such as low production efficiency, serious environmental pollution, high cost of soda ash and caustic soda and low yield of sodium nitrate, which is difficult to meet the growing market demand and strict environmental protection requirements.
Sodium chloride and nitric acid are used as reactants, and the temperature is increased step by step and the temperature range is controlled. The cooling rate is between 5-10°C/min, and the neutralization treatment is carried out to obtain high-purity sodium nitrate.
It has achieved short process route, high production efficiency, no side reactions, and no three waste emissions. The purity of sodium nitrate reaches ≥99.8%, and the yield reaches more than 95.5%, meeting market demand and environmental protection requirements.
Smart Images
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Abstract
Description
Technical Field
[0001] The present application relates to the field of chemical manufacturing technology, and in particular to sodium nitrate and a preparation process thereof. Background Art
[0002] Sodium nitrate is an inorganic salt that exists in nature mainly in the form of saltpeter ore, and its main production area is Chile in South America. At present, sodium nitrate has been widely used in the preparation of chemicals such as nitric acid and sodium nitrite, ingredients in glass, matches, enamel or ceramic industries, catalysts in sulfuric acid industry, and agricultural fertilizers due to its excellent performance. However, as the use of sodium nitrate becomes more and more extensive, its demand is increasing, and artificial synthesis of sodium nitrate has become the main way to obtain sodium nitrate.
[0003] At present, the industrial production methods of sodium nitrate mainly include the following: one is to use nitric acid and soda ash or caustic soda for neutralization reaction, and then obtain sodium nitrate through evaporation, cooling, crystallization and other processes; however, this method has problems such as low production efficiency, serious environmental pollution, and high cost of soda ash and caustic soda, which is difficult to meet environmental protection requirements and market demand. Another method is to use calcium nitrate and sodium sulfate for double decomposition reaction to prepare sodium nitrate, but the sodium nitrate prepared by the above method is easily mixed with calcium nitrate or sodium sulfate, which is usually difficult to remove, resulting in a sodium nitrate yield of less than 95%; in addition, the above process is complicated, and the repeated concentration and crystallization of post-treatment will consume a lot of steam, which is economically and environmentally poor.
[0004] Therefore, in order to meet the growing market demand and increasingly stringent environmental protection requirements, it is particularly important to explore an efficient and environmentally friendly method for preparing sodium nitrate. Summary of the invention
[0005] In order to overcome the problems of low production efficiency, poor economic and environmental protection in the existing preparation process of sodium nitrate, the present application provides a sodium nitrate and a preparation process thereof.
[0006] In a first aspect, the present application provides a process for preparing sodium nitrate, which adopts the following technical solution: A process for preparing sodium nitrate comprises the following steps: (1) mixing a sodium chloride solution and a nitric acid solution, adding water, and obtaining a reaction solution; (2) The reaction solution is heated according to the following procedure: The first stage: heating at a rate of 2-3℃ / min. When the temperature reaches 40-45℃, stop heating and keep warm for 30-60min. The second stage: heating at a heating rate of 0.3-0.5℃ / min. When the temperature reaches 65-70℃, stop heating and keep warm for 60-90min. The third stage: heating at a heating rate of 0.1-0.2℃ / min. When the temperature reaches 85-90℃, stop heating and keep warm for 60-90min. The fourth stage: heating at a heating rate of 1-2°C / min. When the temperature reaches 100-105°C, stop heating and keep warm for 10-30 minutes. (3) The reaction solution is cooled, neutralized, and post-treated to obtain sodium nitrate.
[0007] The present application provides a preparation process of sodium nitrate, wherein the preparation process uses sodium chloride and nitric acid as reactants, and obtains sodium nitrate with a purity of ≥99.8% through a four-stage temperature-controlled reaction. Compared with the preparation process of sodium nitrate in the related art, the preparation process of sodium nitrate provided by the present application 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.
[0008] In the present application, by carrying out four-stage control to the reaction temperature, on the one hand, energy waste is reduced, and the danger caused by the reaction being too violent is effectively avoided, and safety and economic environmental protection are good; on the other hand, by gradually heating up, a stable thermal environment can be continuously provided for the system, thereby increasing the distance between each ion and the degree of freedom of ion activity, so that more sodium ions and nitrate radicals collide effectively, and then quickly and fully form stable nitrates. In addition, in the synthesis process of sodium nitrate, step-by-step heating can control the saturation and supersaturation of the system, and by controlling the temperature of step-by-step heating within the above range, sodium nitrate crystals with higher purity and larger particles can be obtained.
[0009] In some embodiments, the heating rate of the first stage may be 1-2.5° C. / min or 2.5-3° C. / min.
[0010] In a specific embodiment, the heating rate of the first stage may also be 1°C / min, 2.5°C / min or 3°C / min.
[0011] In a specific embodiment, the temperature after the first stage of heating can be 40°C or 45°C.
[0012] In a specific embodiment, the insulation time of the first stage can be 30 min or 60 min.
[0013] In some embodiments, the heating rate of the second stage may be 0.3-0.4° C. / min or 0.4-0.5° C. / min.
[0014] In a specific embodiment, the heating rate of the second stage may also be 0.3°C / min, 0.4°C / min or 0.5°C / min.
[0015] In a specific embodiment, the temperature after the second stage of heating can be 60°C or 65°C.
[0016] In a specific embodiment, the insulation time of the second stage can be 60 min or 90 min.
[0017] In a specific embodiment, the heating rate of the third stage may also be 0.1° C. / min or 0.2° C. / min.
[0018] In a specific embodiment, the temperature after the third stage of heating can be 85°C or 90°C.
[0019] In a specific embodiment, the insulation time of the third stage can be 60 min or 90 min.
[0020] In some embodiments, the heating rate of the fourth stage may be 1-1.5° C. / min or 1.5-2° C. / min.
[0021] In a specific embodiment, the heating rate of the fourth stage can also be 1°C / min, 1.5°C / min or 2°C / min.
[0022] In a specific embodiment, the temperature after the fourth stage of heating can be 105°C.
[0023] In a specific embodiment, the insulation time of the fourth stage can be 10 minutes or 30 minutes.
[0024] Optionally, in step (1), the weight ratio of sodium chloride to nitric acid is 1:(1-1.1), and the amount of water added is 4.5-5.5 times the total weight of sodium chloride and nitric acid.
[0025] In a specific embodiment, the weight ratio of sodium chloride to nitric acid is 1:1.077.
[0026] In a specific embodiment, the amount of water added is 5 times the total weight of sodium chloride and nitric acid.
[0027] Optionally, the concentration of the sodium chloride solution is 22-25wt%, and the concentration of the nitric acid solution is 56-64wt%.
[0028] In a specific embodiment, the concentration of the sodium chloride solution is 24 wt %, and the concentration of the nitric acid solution is 60 wt %.
[0029] Optionally, the cooling rate is 5-10°C / min.
[0030] In some embodiments, the cooling rate can be 3-5°C / min, 3-8°C / min, 3-10°C / min, 3-12°C / min, 5-8°C / min, 5-10°C / min, 5-12°C / min, 8-10°C / min, 8-12°C / min or 10-12°C / min.
[0031] In a specific embodiment, the cooling rate can also be 3°C / min, 5°C / min, 8°C / min, 10°C / min or 12°C / min.
[0032] In the present application, the inventors found that the cooling rate has a certain influence on the yield and purity of sodium nitrate. When the cooling rate is too slow, the yield of the obtained sodium nitrate is low; when the cooling rate is too fast, the yield and purity of the obtained sodium nitrate are both 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 the obtained sodium nitrate.
[0033] Optionally, the temperature after cooling is -20 to 0°C.
[0034] 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 sodium nitrate solution, and then adding sodium hydroxide for neutralization, so that the pH of the material is 6.8-7.
[0035] Optionally, the temperature of the sodium chloride solution and the nitric acid solution is less than 30°C.
[0036] Optionally, the sodium nitrate preparation process is carried out in an acid-resistant reactor capable of providing heating and stirring, and a nozzle for discharging HCl gas is provided on the lid of the reactor, and the nozzle is connected to an acid-resistant pipeline leading to a hydrochloric acid absorption device.
[0037] In a second aspect, the sodium nitrate obtained by the preparation process of sodium nitrate provided in the present application.
[0038] Optionally, the purity of the sodium nitrate is ≥99.8%.
[0039] In summary, this application has the following beneficial effects: 1. The preparation process of sodium nitrate provided in the present application uses sodium chloride and nitric acid as reactants, and obtains sodium nitrate with a purity of ≥99.8% through a four-stage temperature-controlled reaction.
[0040] 2. The preparation process of sodium nitrate provided in this application 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.
[0041] 3. In the preparation process of sodium nitrate provided in the present application, the mother liquor produced by centrifugation can be fully used for recycling production; the generated HCl gas is absorbed by a hydrochloric acid absorption device to obtain hydrochloric acid, and the by-product can be sold.
[0042] 4. The present application further controls the cooling rate within the range of 5-10°C / min, and the yield and purity of the obtained sodium nitrate are higher. The yield of sodium nitrate can reach more than 95.5%, and the purity can reach more than 99.90%. DETAILED DESCRIPTION
[0043] The present application provides a process for preparing sodium nitrate, comprising the following steps: (1) adding 22-25wt% sodium chloride solution and 56-64wt% nitric acid solution into a reaction kettle in proportion and stirring evenly; then adding water 4.5-5.5 times the total weight of sodium chloride and nitric acid, heating and reacting; wherein the weight ratio of sodium chloride to nitric acid is 1:(1-1.1).
[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 2-3℃ / min. When the temperature reaches 40-45℃, stop heating and keep warm for 30-60min. The second stage: heating at a heating rate of 0.3-0.5℃ / min. When the temperature reaches 65-70℃, stop heating and keep warm for 60-90min. The third stage: heating at a heating rate of 0.1-0.2℃ / min. When the temperature reaches 85-90℃, stop heating and keep warm for 60-90min. The fourth stage: heating at a heating rate of 1-2°C / min. When the temperature reaches 100-105°C, stop heating and keep warm for 10-30 minutes.
[0045] (3) The reaction kettle is gradually cooled down, and stirring is continued during the cooling process until the temperature drops to -20 to 0°C to obtain a reaction solution.
[0046] (4) The reaction solution is centrifuged and filtered using an acid-resistant centrifuge, and the obtained material is added to a neutralization kettle pre-filled with sodium nitrate solution, and then sodium hydroxide is added for neutralization, so that the pH of the material is 6.8-7.
[0047] (5) The neutralized material is centrifuged, washed, and dried to obtain sodium nitrate.
[0048] In the above preparation process, the mother liquor obtained from the two centrifugations can be collected and recycled in subsequent production; 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 respectively provide a preparation process of sodium nitrate.
[0052] The difference between the above embodiments is that: in the heating process in step (2), the temperature control in the four-stage heating process is specifically shown in Table 1 below.
[0053] The preparation process of sodium nitrate provided in Examples 1-15 comprises the following steps: (1) 12 kg of sodium chloride was dissolved in 50 kg of water to obtain a 24 wt% sodium chloride solution; 12.9 kg of nitric acid was dissolved in 21.5 kg of water to obtain a 60 wt% nitric acid solution; the sodium chloride solution and the nitric acid solution were added to a reactor and stirred evenly; then 124.5 kg of water was added to the reactor.
[0054] (2) The reactor is slowly heated by a jacket or coil, and the temperature control during the four-stage heating process is shown in Table 1. (The heating rates of the four stages are respectively represented by V1, V2, V3, and V4; the temperatures after the heating of the four stages are respectively represented by T1, T2, T3, and T4; the holding times after the heating of the four stages are respectively represented by t1, t2, t3, and t4) (3) The reactor was gradually cooled down with continuous stirring during the cooling process, and the cooling rate was controlled at 8°C / min until the temperature dropped to -20°C to obtain a reaction solution.
[0055] (4) The reaction solution is centrifuged and filtered using an acid-resistant centrifuge, and the obtained material is added to a neutralization kettle pre-filled with sodium nitrate solution, and then sodium hydroxide is added for neutralization, so that the pH of the material is 6.8-7.
[0056] (5) The neutralized material is centrifuged, washed, and dried to obtain sodium nitrate.
[0057] Comparative Examples 1-7 Comparative Examples 1-7 respectively provide a preparation process of sodium nitrate.
[0058] The difference between the above comparative example and Example 2 is that: in the heating process in step (2), the temperature control in the four-stage heating process is specifically shown in Table 1 below.
[0059] Table 1 Temperature control during the four-stage heating process in the preparation methods provided in Examples 1-15 and Comparative Examples 1-7 Examples 16-19 Examples 16-19 respectively provide a process for preparing sodium nitrate.
[0060] The difference between the above embodiment and embodiment 1 is that the cooling rate during the cooling process is specifically shown in Table 2 below.
[0061] Table 2 Cooling rate in the preparation process provided by Example 2 and Examples 16-19 Example Cooling rate (℃ / min) 2 8 16 3 17 5 18 10 19 12 Performance test Sodium nitrate was prepared using the sodium nitrate preparation process provided in Example 1-19 and Comparative Example 1-7, and the mass yield of sodium nitrate was calculated, and the purity of sodium nitrate was tested. The results are shown in Table 3 below.
[0062] The purity of sodium nitrate was detected by acid-base titration; the calculation formula of the mass yield of sodium nitrate was: mass yield of sodium nitrate=actual output of sodium nitrate / theoretical output of sodium nitrate×100%.
[0063] Table 3 Mass yield and purity test results of sodium nitrate obtained in Examples 1-19 and Comparative Examples 1-7 According to the test results in Table 3, the yield of sodium nitrate obtained in Examples 1-15 of the present application is 94.2-96.5%, and the purity is 99.82-99.96%; while the yield of sodium nitrate obtained in Comparative Examples 6-7 is only 86.2-91.7%, and the purity is only 90.35-93.68%. Therefore, it is shown that the present application adopts a four-stage step-by-step heating method to obtain high-yield and high-purity sodium nitrate.
[0064] It can be seen from the test results of Examples 1-3 and Comparative Examples 1-2 that the heating rate in the first stage has a significant effect on the yield and purity of sodium nitrate. When the heating rate in the first stage is controlled to 2-3°C / min in Example 1-3, the yield of sodium nitrate obtained is 94.2-96.4%, and the purity is 99.82-99.94%; while when the heating rate in the first stage is controlled to 1 or 3.5°C / min in Comparative Example 1-2, the yield of sodium nitrate obtained is only 91.5-93.2%, and the purity is only 97.34-98.79%. Therefore, it is explained that the application controls the heating rate in the first stage within the range of 2-3°C / min, and the yield and purity of the obtained sodium nitrate are high.
[0065] The test results of Examples 1-15 and Comparative Example 3 show that when the terminal temperature after each stage of heating is controlled within the range of 40-45°C, 65-70°C, 85-90°C, and 100-105°C in Example 1-15, the yield of sodium nitrate obtained is 94.2-96.5%, and the purity is 99.82-99.96%; while when the terminal temperature after each stage of heating is controlled within the range of 50°C, 75°C, 95°C, and 110°C in Comparative Example 3, the yield of sodium nitrate obtained is only 93.8%, and the purity is only 94.25%. Therefore, it is explained that the temperature after each stage of heating will affect the yield and purity of sodium nitrate. The present application controls the terminal temperature after each stage of heating within the range of 40-45°C, 65-70°C, 85-90°C, and 100-105°C, and the yield and purity of sodium nitrate obtained are high.
[0066] The test results of Examples 1-15 and Comparative Example 4 show that when the heating rate of each stage in Example 1-15 is controlled within the range of 2-3°C / min, 0.3-0.5°C / min, 0.1-0.2°C / min, and 1-2°C / min, the yield of sodium nitrate obtained is 94.2-96.5%, and the purity is 99.82-99.96%; while when the heating rate of each stage in Comparative Example 4 is controlled to 0.4°C / min, 0.8°C / min, 1.2°C / min, and 1.5°C / min, the yield of sodium nitrate obtained is only 91.3%, and the purity is only 94.62%. Therefore, it is explained that the heating rate of each stage will affect the yield and purity of sodium nitrate. The present application controls the heating rate of each stage within the range of 2-3°C / min, 0.3-0.5°C / min, 0.1-0.2°C / min, and 1-2°C / min, and the yield and purity of sodium nitrate obtained are high.
[0067] The test results of Examples 1-15 and Comparative Example 4 show that when the holding time of each stage in Example 1-15 is controlled within the range of 30-60min, 60-90min, 60-90min, and 10-30min, the yield of sodium nitrate obtained is 94.2-96.5%, and the purity is 99.82-99.96%; while when the holding time of each stage in Comparative Example 5 is controlled to 30min, the yield of sodium nitrate obtained is only 92.0%, and the purity is only 92.17%. Therefore, it is explained that the yield and purity of sodium nitrate obtained by controlling the holding time of each stage in the present application within the range of 30-60min, 60-90min, 60-90min, and 10-30min are high.
[0068] It can be seen from the test results of Example 2 and Examples 16-19 that as the cooling rate increases, the yield of the obtained sodium nitrate shows a trend of first increasing and then decreasing, and the purity shows a trend of gradually decreasing; among them, the yield of sodium nitrate obtained in Example 2 and Examples 17-18 is 95.8-96.4% (>95.5%), and the purity is 99.92-99.94% (>99.90%); while the yield of sodium nitrate obtained in Example 16 is only 94.9%; the yield of sodium nitrate obtained in Example 19 is only 94.6%, and the purity is only 99.87%. Therefore, it is explained that the present application further controls the cooling rate in the cooling process within the range of 5-10°C / min, and the yield and purity of the obtained sodium nitrate are higher.
[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 process for preparing sodium nitrate, characterized in that: The following steps are involved: (1) mixing a sodium chloride solution and a nitric acid solution, and adding water to obtain a reaction solution; (2) Heat the reaction solution according to the following procedure: The first stage: heating at a rate of 2-3℃ / min. When the temperature reaches 40-45℃, stop heating and keep warm for 30-60min. The second stage: heating at a heating rate of 0.3-0.5℃ / min. When the temperature reaches 65-70℃, stop heating and keep warm for 60-90min. The third stage: heating at a heating rate of 0.1-0.2℃ / min. When the temperature reaches 85-90℃, stop heating and keep warm for 60-90min. The fourth stage: heating at a heating rate of 1-2°C / min. When the temperature reaches 100-105°C, stop heating and keep warm for 10-30 minutes. (3) The reaction solution is cooled, neutralized, and post-treated to obtain sodium nitrate.
2. The preparation process of sodium nitrate according to claim 1, characterized in that: In the step (1), the weight ratio of sodium chloride to nitric acid is 1:(1-1.1), and the amount of water added is 4.5-5.5 times the total weight of sodium chloride and nitric acid.
3. The preparation process of sodium nitrate according to claim 1, characterized in that, The concentration of the sodium chloride solution is 22-25wt%, and the concentration of the nitric acid solution is 56-64wt%.
4. The preparation process of sodium nitrate according to claim 1, characterized in that: The cooling rate is 5-10°C / min.
5. The process for preparing sodium nitrate according to claim 1, characterized in that: The temperature after cooling is -20~0℃.
6. The process for preparing sodium nitrate according to claim 5, characterized in that: The specific steps of the neutralization are: centrifugally filtering the cooled reaction solution, adding the obtained material into a neutralization kettle pre-placed with sodium nitrate solution, and then adding sodium hydroxide for neutralization, so that the pH of the material is 6.8-7.
7. The process for preparing sodium nitrate according to claim 1, characterized in that: The temperature of the sodium chloride solution and the nitric acid solution is less than 30°C.
8. The process for preparing sodium nitrate according to any one of claims 1 to 7, characterized in that: The sodium nitrate preparation process is carried out in an acid-resistant reactor capable of providing heating and stirring. The lid of the reactor is provided with a pipe opening for discharging HCl gas, and the pipe opening is connected to an acid-resistant pipeline leading to a hydrochloric acid absorption device.
9. Sodium nitrate obtained by the preparation process of the sodium nitrate described in any one of claims 1 to 8.
10. The sodium nitrate according to claim 9, characterized in that The purity of the sodium nitrate is ≥99.8%.