A method for preparing needle-shaped potassium sulfamate crystals

Abstract

The invention discloses a preparation method of needle-shaped potassium sulfamate for the synthesis of ammonium dinitramide, first crushing industrial-grade aqueous potassium sulfamate crystals to 20-50 meshes, drying them in a dynamic vacuum heating at 100-120°C for 12-24 hours, then heating them with an organic solvent by microwave, cooling naturally, filtering, and drying them in a dynamic vacuum heating at 50-80°C for 12-24 hours to obtain needle-shaped potassium sulfamate. The present invention is easy to operate, and the organic solvent used can be reused after filtration recovery, does not produce aqueous organic waste liquid, saves costs, and is beneficial to environmental protection; the obtained needle-shaped potassium sulfamate is used for the synthesis of ammonium dinitramide, and the yield can reach more than 60%, which is significantly higher than untreated industrial-grade aqueous potassium sulfamate crystals, and can be used for the pretreatment of raw materials for the industrial production of ammonium dinitramide.

Description

Technical Field

[0001] The invention belongs to the technical field of ammonium dinitramide synthesis, and in particular relates to a method for preparing anhydrous potassium aminosulfonate used as a raw material for ammonium dinitramide synthesis. Background Art

[0002] Ammonium dinitramide (ADN) is a new type of high-energy oxidant with a molecular formula of NH4N(NO2)2, a heat of generation of -149kJ / mol, and an oxygen balance of 25.81%. Its molecule contains both fuel and oxidant components, and can be used as both explosive and propellant oxidant. Compared with the traditional solid oxidant ammonium perchlorate (AP, NH4ClO4, heat of generation -295.8kJ / mol), ADN molecules do not contain halogens, and the combustion products are smokeless. Replacing AP with it can not only increase energy, but also reduce characteristic signals and improve stability. Some literature believes that when ADN is used in low-characteristic signal propellants, the specific impulse can be increased by 7%, and when it is used in aluminum-containing propellants, the specific impulse can be increased by 10%. As a new type of oxidant, ADN can be used not only in small surface-to-air missiles, but also in boosters of intercontinental missiles. It is one of the most promising new generation of high-energy components of solid propellants in the future. ADN has good water solubility and is much less toxic than hydrazine. It can be used in water-containing green unit propellants. It has the advantages of high energy, low toxicity, environmental protection, and good safety, and is expected to replace hydrazine-based propellants.

[0003] At present, the synthesis of ADN mainly adopts inorganic method, using ammonium sulfamate or potassium sulfamate as raw materials, fuming nitric acid as nitrating agent, and concentrated sulfuric acid as catalyst. The raw materials are cheap and easy to obtain, the operation is simple, and it is suitable for industrial production. Among them, ammonium sulfamate has poor thermal stability, and it will explode when heated, producing toxic nitrogen and sulfur oxide gases, while potassium sulfamate has much better thermal stability. Therefore, the industrial production of ammonium dinitramide mostly uses potassium sulfamate as raw material, such as the FOI process in Sweden.

[0004] NH2SO3K→Mixed acid nitration→HN(NO2)2+KOH→KN(NO2)2+(NH4)2SO4→NH4N(NO2)2

[0005] The method for preparing potassium sulfamate that can be used for the synthesis of ammonium dinitramide disclosed in patents such as US5976483 is to neutralize sulfamate with potassium hydroxide to prepare a potassium sulfamate aqueous solution, then add the aqueous solution to ethanol to promote the precipitation of potassium sulfamate solid, filter, rinse with ethanol, heat and dry at 70°C, and finally grind the dried solid into fine powder. The method reported by Wooram Kim et al. (Journal of Energetic Materials, 2017 (35), 1, 44-52) is basically the same as the above method, except that a different organic solvent (such as acetone, etc.) is used. The disadvantage of the above method is that a large amount of aqueous organic waste liquid is generated. Since organic solvents such as ethanol are difficult to separate from water, recovery is difficult and costly, so this method is difficult to apply to industrial production.

[0006] Currently, potassium sulfamate is a common chemical that is cheap and easy to obtain, and there is no need to prepare it by yourself. However, the yield of using it directly in the synthesis of ammonium dinitramide is low. For example, Wooram Kim et al. reported that the yield of synthesizing ammonium dinitramide using the commercial potassium sulfamate mixed acid method was only 31.3%. Summary of the invention

[0007] The invention discloses a pretreatment method for commercial potassium sulfamate, which is a pretreatment method for potassium sulfamate, a raw material for synthesizing ammonium dinitramide. The obtained needle-shaped potassium sulfamate crystals are used for synthesizing ammonium dinitramide by a mixed acid method, and the yield can reach more than 60%. The invention is simple to operate, and the organic solvent can be reused, and can be used for the pretreatment of raw materials for industrial production of ammonium dinitramide.

[0008] In order to achieve the above technical effects, the technical solution adopted by the present invention is:

[0009] A method for preparing needle-shaped potassium sulfamate crystals. The purpose of the invention is to provide a pretreatment method for potassium sulfamate, a raw material for the synthesis of ammonium dinitramide, comprising the steps of crushing the aqueous potassium sulfamate crystals, vacuum heating and drying, microwave heating treatment with an organic solvent, and vacuum heating and drying again;

[0010] The pulverization of the aqueous potassium sulfamate crystals is to pulverize the commercially available 98% potassium sulfamate aqueous crystals into 20-50 meshes;

[0011] The vacuum heating drying is to place the crushed potassium aminosulfonate in a dynamic vacuum heating drying device and dry it at 100-120° C. for 12-24 hours;

[0012] The organic solvent microwave heating treatment is to add the heated and dried potassium sulfamate into the organic solvent, and microwave heat it to 80-140° C., and continue in this state for 4-8 hours;

[0013] The organic solvent used in the organic solvent microwave heating treatment includes one or more of ethanol, isopropanol, n-butanol, acetonitrile, dimethylformamide, and dimethyl sulfoxide, and the amount used is 2-4 liters per kilogram of potassium sulfamate;

[0014] The second vacuum heating and drying is to place the potassium aminosulfonate after microwave heating with an organic solvent in a dynamic vacuum heating drying device and dry it at 50 to 80° C. for 24 to 48 hours.

[0015] The preparation process of a needle-shaped potassium sulfamate crystal of the invention comprises the following steps: crushing 98% of commercially available potassium sulfamate water-containing crystals into 20-50 meshes, placing the crystals in a dynamic vacuum heating drying device, and drying the crystals at 100-120 DEG C for 12-24 hours; placing the dried potassium sulfamate in an organic solvent, heating the crystals to 80-100 DEG C with microwaves, and heating the dried crystals for 4-8 hours; cooling the dried crystals naturally, and filtering to remove the organic solvent; placing the filtered solids in a dynamic vacuum heating drying device, and drying the dried crystals at 50-80 DEG C for 24-48 hours to obtain white needle-shaped potassium sulfamate crystals.

[0016] The invention is easy to operate, the organic solvent used can be reused after being filtered and recovered, no aqueous organic waste liquid is generated, cost is saved, and it is environmentally friendly; the needle-shaped potassium sulfamate is used for the synthesis of ammonium dinitramide, and the yield can reach more than 60%, which is significantly higher than that of untreated industrial-grade aqueous potassium sulfamate crystals, and can be used for the pretreatment of raw materials for the industrial production of ammonium dinitramide.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention uses cheap and readily available commercial aqueous potassium sulfamate to prepare potassium sulfamate needle-shaped crystals, which are used for the synthesis of ammonium dinitramide by a mixed acid process, with a yield of more than 60%, which helps to reduce the production cost of ammonium dinitramide.

[0019] 2. The present invention abandons the conventional recrystallization method of first preparing an aqueous solution and then promoting solid precipitation with an organic solvent, thereby avoiding the formation of aqueous organic waste liquid; the organic solvent used in the present invention can be reused after filtration and recovery, which is beneficial to environmental protection, saves costs, and is easy for industrial production.

[0020] 3. The present invention is easy to operate, and the organic solvent used can be reused after being filtered and recovered, and no aqueous organic waste liquid is generated, which saves costs and is environmentally friendly; the obtained needle-shaped potassium sulfamate is used for the synthesis of ammonium dinitramide, and the yield can reach more than 60%, which is significantly higher than that of untreated industrial-grade aqueous potassium sulfamate crystals, and can be used for the pretreatment of raw materials for the industrial production of ammonium dinitramide. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1The crystal of Example 1 of the present invention Figure 1 .

[0022] Figure 2 The crystal of Example 1 of the present invention Figure 2 . DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with specific embodiments.

[0024] Example 1

[0025] 10.0 kg of potassium sulfamate (98% by mass potassium sulfamate containing water, the same below) crystals were crushed to 20 mesh, placed in a dynamic vacuum heating drying device (vacuubrand, MV 10C NT VARIO, the same below), and dried at 120°C for 24 hours (vacuum degree of 8-9 mba). The dried potassium sulfamate was placed in 30 liters of ethanol, microwave heated to 80°C, and maintained for 8 hours. The above solid-liquid mixture was naturally cooled to room temperature, filtered, and placed in a dynamic vacuum heating drying device, dried at 60°C for 24 hours (vacuum degree of 8-9 mba), to obtain 9.12 kg of white needle-shaped (length 1-3 mm, thickness 0.01-0.03 mm, width 0.1-0.3 mm at one end, and irregular needle-shaped at the other end) crystals (see attached Figure 1 , attached Figure 2 , the same below).

[0026] Example 2

[0027] 10.0 kg of potassium sulfamate (98%) crystals were crushed to 40 mesh, placed in a dynamic vacuum heating drying device, and dried at 110° C. for 20 hours (vacuum degree is 8-9 mba). The dried potassium sulfamate was placed in 20 liters of dimethylformamide, microwave heated to 130° C., and maintained for 5 hours. The above solid-liquid mixture was naturally cooled to room temperature, filtered, placed in a dynamic vacuum heating drying device, and dried at 80° C. for 48 hours (vacuum degree is 8-9 mba), and 9.31 kg of white needle-shaped (length 1-3 mm, thickness 0.01-0.03 mm, width 0.1-0.3 mm at one end, and irregular needle-shaped at the other end) crystals were obtained.

[0028] Example 3

[0029] 10.0 kg of potassium sulfamate (98%) crystals were crushed to 50 mesh, placed in a dynamic vacuum heating drying device, and dried at 100° C. for 12 hours (vacuum degree is 8-9 mba). The dried potassium sulfamate was placed in 40 liters of n-butanol, microwave heated to 100° C., and maintained for 8 hours. The above solid-liquid mixture was naturally cooled to room temperature, filtered, placed in a dynamic vacuum heating drying device, and dried at 70° C. for 36 hours (vacuum degree is 8-9 mba), and 9.35 kg of white needle-shaped (length 1-3 mm, thickness 0.01-0.03 mm, width 0.1-0.3 mm at one end, and irregular needle-shaped at the other end) crystals were obtained.

[0030] Example 4

[0031] 10.0 kg of potassium sulfamate (98%) crystals were crushed to 20 mesh, placed in a dynamic vacuum heating drying device, and dried at 100° C. for 12 hours (vacuum degree is 8-9 mba). The dried potassium sulfamate was placed in 30 liters of acetonitrile, microwave heated to 80° C., and maintained for 4 hours. The above solid-liquid mixture was naturally cooled to room temperature, filtered, placed in a dynamic vacuum heating drying device, and dried at 50° C. for 24 hours (vacuum degree is 8-9 mba), and 9.35 kg of white needle-shaped (length 1-3 mm, thickness 0.01-0.03 mm, width 0.1-0.3 mm at one end, and irregular needle-shaped at the other end) crystals were obtained.

[0032] Example 5

[0033] 10.0 kg of potassium sulfamate (98%) crystals were crushed to 50 mesh, placed in a dynamic vacuum heating drying device, and dried at 120° C. for 20 hours (vacuum degree is 8-9 mba). The dried potassium sulfamate was placed in 40 liters of dimethyl sulfoxide, microwave heated to 150° C., and maintained for 8 hours. The above solid-liquid mixture was naturally cooled to room temperature, filtered, placed in a dynamic vacuum heating drying device, and dried at 80° C. for 48 hours (vacuum degree is 8-9 mba), and 9.17 kg of white needle-shaped (length 1-3 mm, thickness 0.01-0.03 mm, width 0.1-0.3 mm at one end, and irregular needle-shaped at the other end) crystals were obtained.

[0034] Example 6

[0035] 10.0 kg of potassium sulfamate (98%) crystals were crushed into 30 meshes, placed in a dynamic vacuum heating drying device, and dried at 110°C for 16 hours (vacuum degree is 8-9 mba). The dried potassium sulfamate was placed in 30 liters of isopropanol, microwave heated to 80°C, and maintained for 8 hours. The above solid-liquid mixture was naturally cooled to room temperature, filtered, placed in a dynamic vacuum heating drying device, and dried at 70°C for 24 hours (vacuum degree is 8-9 mba), and 9.41 kg of white needle-shaped (length 1-3 mm, thickness 0.01-0.03 mm, width 0.1-0.3 mm at one end, and irregular needle-shaped at the other end) crystals were obtained.

[0036] Comparative Example 1

[0037] 281.4g of aminosulfonic acid is suspended in 200ml of water, 176g of potassium hydroxide is dissolved in 200ml of water, and the potassium hydroxide aqueous solution is slowly added to the aminosulfonic acid suspension under stirring. The above reaction solution is added to 600ml of anhydrous ethanol, the resulting precipitate is filtered, rinsed with anhydrous ethanol, and the above precipitate is placed in a vacuum heating drying oven and dried at 70°C for 48 hours (vacuum degree is 8-9mba). The white powdery solid obtained after drying is ground into 20 mesh using a ball mill.

[0038] Comparative Example 2

[0039] 350g of aminosulfonic acid is suspended in 500ml of water, and 240g is dissolved in 500ml of water. Under stirring, potassium hydroxide aqueous solution is slowly added to the aminosulfonic acid suspension. 1500ml of acetone is slowly added to the above reaction aqueous solution at room temperature, the obtained precipitate is filtered, rinsed with acetone, and the above precipitate is placed in a vacuum heating drying oven and dried at 70°C for 48 hours (vacuum degree is 8-9mba). The white powdery solid obtained after drying is ground into 20 mesh using a ball mill.

[0040] Control experiment

[0041] In a liquid nitrogen-ethanol cold bath, 400 ml of concentrated sulfuric acid (mass concentration 98%) was slowly added to 1700 ml of fuming nitric acid (mass content 96%). Control the temperature at -40°C, add 550 g of potassium sulfamate to the mixed acid in two equal batches under rapid stirring, and react for 20 minutes after all the addition is completed. Pour the reaction mixture into crushed ice for dilution. The resulting dilution was neutralized with ammonia water at -20°C, and the content of the product ammonium dinitramide was determined by ion chromatography. The crystals obtained in Examples 1 to 6, Comparative Examples 1 to 2, and untreated commercial potassium sulfamate were used as potassium sulfamate raw materials for this process, and the results are as follows:

[0042]

[0043]

[0044] It can be seen from the results in the table that the control experimental yields of the potassium sulfamate raw materials prepared by the technology adopted in the present invention, Examples 1 to 6, are significantly higher than those of the potassium sulfamate raw materials prepared by the prior art (Comparative Examples 1 to 2), and can reach a maximum experimental yield of 67.2% (Example 5), which is much higher than that of the untreated commercial potassium sulfamate raw materials.

[0045] The above examples are merely embodiments with better effects, and are not intended to further limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. that can be easily implemented by those familiar with the art should be included in the scope of protection of the present invention.

Claims

1. A method for preparing needle-shaped potassium sulfamate crystals, characterized in that: The following steps are involved: The aqueous potassium aminosulfonate crystals are crushed, vacuum heated and dried, subjected to microwave heating with an organic solvent, and vacuum heated and dried again; The vacuum heating drying is to place the crushed potassium sulfamate in a dynamic vacuum heating drying device and dry it at 100-120° C. for 12-24 hours; The organic solvent microwave heating treatment is to add the heated and dried potassium sulfamate into the organic solvent, and microwave heat it to 80-140° C., and continue in this state for 4-8 hours; The second vacuum heating and drying is to place the potassium sulfamate treated with microwave heating of the organic solvent in a dynamic vacuum heating drying device, and dry it at 50-80° C. for 24-48 hours to obtain needle-shaped potassium sulfamate crystals.

2. The preparation method according to claim 1, characterized in that: The pulverization of the aqueous potassium sulfamate crystals is to pulverize the commercially available potassium sulfamate aqueous crystals with a mass content of 95%-98% to 20-50 meshes.

3. The preparation method according to claim 1, characterized in that: The organic solvent used in the organic solvent microwave heating treatment includes one or more of ethanol, isopropanol, n-butanol, acetonitrile, dimethylformamide, and dimethyl sulfoxide, and the usage amount is 2-4 liters per kilogram of potassium aminosulfonate raw material.

4. The preparation method according to claim 1, characterized in that: When the organic solvent is subjected to microwave heating, the microwave heating is performed to 100-120° C. and is continued in this state for 4-8 hours.

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