A method for preparing high-quality sulfamic acid from fuming sulfuric acid as raw material

Abstract

The application is a method for preparing high-quality sulfamic acid by using fuming sulfuric acid as raw material, and belongs to the field of sulfamic acid preparation. Through the cooperation of the introduction of multifunctional composite additives composed of reaction stabilizers, metal ion masking agents and crystallization regulators and the optimization of reaction-crystallization process, the synthesis reaction is ensured to be stable and efficient by first adding low-temperature and then using reaction heat to warm up. In the purification stage, the flash evaporation assisted recrystallization technology is adopted, combined with the dissolution of specific concentration of dilute sulfuric acid and rapid crystallization, so as to efficiently separate impurities and obtain high-purity crystals. Through the synergistic effect of the composite additives, the generation of organic by-products is inhibited from the source, and the incorporation path of metal ion impurities is effectively blocked, so that the product purity of sulfamic acid can be comprehensively and significantly improved, the metal impurities can be reduced, and the yield can be improved.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a method for preparing high-quality aminosulfonic acid, and particularly to a process method for the clean production of high-purity, high-quality aminosulfonic acid by introducing trace amounts of composite additives to regulate the reaction pathway, inhibit impurity generation, and improve the crystallization process. Background Technology

[0002] Aminosulfonic acid is an important strong inorganic acid widely used in various industrial fields such as metal cleaning, chlorine dioxide preparation, resin crosslinking, electroplating, and the synthesis of pesticides and flame retardants. Its industrial production mainly adopts the process route of reacting urea with fuming sulfuric acid. This route is a mature technology, but controlling the purity, yield, and crystal morphology of the product has always been a difficult technical challenge for the industry.

[0003] The traditional urea-fuming sulfuric acid process involves the following basic chemical reaction: NH₂CONH₂ (urea) + SO₃ (fuming sulfuric acid) + H₂SO₄ → 2NH₂SO₃H (sulfamic acid) + CO₂↑. This reaction is highly exothermic and accompanied by complex side reactions. These side reactions reduce the fuming sulfuric acid content in the reaction system and cause urea loss, thus decreasing the sulfamic acid yield. The extent of these side reactions depends primarily on the reaction temperature and the free sulfur trioxide content in the fuming sulfuric acid. Higher temperatures and higher free sulfur trioxide content result in greater urea oxidation. Existing industrial reactors are large, making precise temperature control difficult; therefore, the current sulfamic acid yield is around 85%, and further improvements are challenging.

[0004] Raw materials such as fuming sulfuric acid, urea, and equipment corrosion may introduce Fe. 3+ Ca 2+ Mg 2+ Al 3+ Metal ions, such as Fe, are easily trapped or adsorbed within or on the surface of aminosulfonic acid crystals in strongly acidic crystal environments, forming colored impurities (e.g., Fe). 3+ This can cause the product to turn yellow or affect indicators such as the product's electrical conductivity.

[0005] Therefore, it is of great significance to develop a new process for the preparation of aminosulfonic acid that can suppress the generation of impurities at the source of the reaction, purify simultaneously during the crystallization process, and not affect the yield of the main reaction. Summary of the Invention

[0006] This invention provides a method for preparing high-quality aminosulfonic acid using fuming sulfuric acid as raw material, which solves the problems of low yield and high impurity content in existing aminosulfonic acid production processes.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for preparing high-quality aminosulfonic acid from fuming sulfuric acid includes the following steps: (1) Dissolve the reaction stabilizer and metal ion masking agent in a solvent to prepare a first dispersion with a mass concentration of 10%-20%; dissolve the crystallization regulator in a solvent to prepare a second dispersion with a mass concentration of 3%-8%, for later use; (2) Add fuming sulfuric acid to the reaction vessel, then add the first dispersion, and stir at 70-80 rpm for 5-15 minutes; (3) Add urea to the reactor, control the rate of urea addition, maintain the material temperature ≤70℃, and use the heat of reaction to raise the material temperature in the reactor to 80-85℃ before the urea addition is nearing completion. After the urea is added, stir at 70-80 rpm for 5-10 minutes and keep warm for 1-2 hours. (4) After the reaction is completed, add the second dispersion to the reaction solution, cool down to 40-45℃, add solvent, maintain the material temperature ≤70℃, adjust the sulfuric acid content to 70%, and after the addition is completed, cool down to 40-45℃ and carry out solid-liquid separation to obtain wet crude aminosulfonic acid and dilute acid with a concentration of 70%. The dilute acid is filtered after precipitation to become an industrial product. (5) The wet crude aminosulfonic acid product is rinsed with deionized water and / or mother liquor. The rinsing solution is then precipitated to become washing water. (6) Stir and heat dilute sulfuric acid and / or mother liquor to 40-45℃ at a speed of 70-80 rpm, add the washed crude aminosulfonic acid, and dissolve it into a transparent liquid under the condition that the material temperature is ≤70℃. Then flash evaporate the liquid. The flash evaporated condensate becomes the mother liquor. Cool the flash evaporated aminosulfonic acid solution to crystallize. The crystallized aminosulfonic acid crystals and liquid flow into a thickener for solid-liquid separation. The separated liquid becomes the mother liquor and the solid is aminosulfonic acid crystals. (7) The aminosulfonic acid crystals are dried under low temperature and vacuum to obtain high-purity aminosulfonic acid product. The gas produced by vacuum drying is condensed to obtain condensate, which becomes the mother liquor.

[0008] Further, preferably: the reaction stabilizer is p-toluenesulfonic acid, and the amount added is 0.2%-0.4% of the urea quality.

[0009] Further, preferably: the metal ion masking agent is one or more of hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid and diethylenetriaminepentamethylidene phosphonic acid, and its addition amount is 0.05%-0.1% of the urea quality.

[0010] Further, preferably: the crystallization regulator is sodium polyacrylate, and its addition amount is 0.01%-0.06% of the urea quality.

[0011] Furthermore, preferably, the mass concentration of free SO3 in the fuming sulfuric acid is 20%-30%.

[0012] Further, preferably, the mass ratio of urea to fuming sulfuric acid is 1:6.0-6.4.

[0013] Further, preferably: the vacuum drying is specifically carried out at 50-70℃ and a vacuum degree below -0.09MPa for 4-6 hours.

[0014] Further, preferably, the solvent is deionized water and / or washing water.

[0015] Furthermore, preferably, the dilute sulfuric acid is a sulfuric acid solution with a sulfuric acid concentration of 5-30%. The beneficial effects of this invention are:

[0016] This invention, through the synergistic effect of composite additives, inhibits the formation of organic byproducts at the source and effectively blocks the incorporation pathway of metal ion impurities. It comprehensively and significantly improves the purity of aminosulfonic acid products, reduces metal impurities, and increases yield. The yield of the obtained aminosulfonic acid product is over 88%, and the aminosulfonic acid content is consistently ≥99.7%, with key impurities such as Fe... 3+ No heavy metals (as Pb) were detected; the mass fraction of heavy metals was <0.001%. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative effort are also described.

[0018] The raw materials used in this invention are as follows: fuming sulfuric acid; free sulfur trioxide (SO3): 24.4%; ash content: 0.001%; ​​iron (Fe): 0.0002%.

[0019] Industrial urea: Total nitrogen (N) mass fraction: 46.1%; Biuret mass fraction: 0.8%; Moisture: 0.5%; Iron (as Fe) mass fraction: 0.0008%; Sulfate (as SO2) mass fraction: 0.018%; Water-insoluble matter mass fraction: 0.036%.

[0020] Sodium polyacrylate: Industrial grade, active ingredient content ≥99%; p-Toluenesulfonic acid: Industrial grade, active ingredient content ≥99%; Hydroxyethylidene diphosphonic acid: Industrial grade, active ingredient content ≥99%.

[0021] Example 1 A method for preparing high-quality aminosulfonic acid using fuming sulfuric acid as raw material, using 200 kg of urea as raw material, with the following addition amounts: fuming sulfuric acid: 1250 kg; p-toluenesulfonic acid: 0.6 kg (0.3%); sodium polyacrylate: 0.12 kg (0.06%); and hydroxyethylidene diphosphonic acid: 0.06 kg (0.03%).

[0022] Includes the following steps: (1) Dissolve the reaction stabilizer and metal ion masking agent in deionized water (use washing water if available) to prepare a first dispersion with a mass concentration of 20%; dissolve the crystallization regulator in deionized water (use washing water if available) to prepare a second dispersion with a mass concentration of 5%, and set aside. (2) Add fuming sulfuric acid to the reactor, start the stirring and cooling system, add the first dispersion to the reactor, stir at 70 rpm, keep the temperature at 40-45℃, and stir for 10 min; (3) Add solid urea to the reactor and control the urea addition rate. When the temperature of the material in the reactor rises to 65°C, turn on the cooling water of the reactor jacket and adjust the urea addition rate to maintain the temperature of the material in the reactor not exceeding 70°C. Before the urea addition is about to end, use the heat of reaction to raise the temperature of the material in the reactor to 80-85°C. After the urea is added, continue stirring for 5 minutes and keep warm for two hours. (4) After the reaction is completed, add the second dispersion to the reaction solution, control the stirring speed at 70 rpm, stir for 10 min, cool down to 40-45℃, add a 5-30% dilute sulfuric acid aqueous solution (use washing water if available), maintain the temperature of the material in the reactor not higher than 70℃, adjust the sulfuric acid content in the reactor to 70%, after the addition is completed, cool down to 45℃, and perform solid-liquid separation to obtain wet crude aminosulfonic acid and dilute acid with a concentration of about 70%. The dilute acid is filtered after precipitation to become an industrial product. (5) Use deionized water (use mother liquor if available) to rinse the wet crude aminosulfonic acid product to displace the sulfuric acid in the wet crude aminosulfonic acid product. The acid concentration of the mother liquor is increased to about 30%. After precipitation, it becomes washing water. (6) Add a 20% dilute sulfuric acid solution (if there is mother liquor) to the dissolving slurry tank, control the stirring speed at 70 r / min, heat to 40-45℃, then add wet crude aminosulfonic acid, control the temperature not to exceed 70℃, and pump it into the enamel dissolving kettle after it is completely dissolved. Steam is introduced into the outer jacket of the kettle to completely dissolve the crude product slurry into a transparent liquid in the shortest time under the condition that the material temperature is not greater than 70℃. Close the steam valve and slowly open the ball valve at the bottom of the enamel dissolving kettle. The completely dissolved crude product solution flows into the dissolving buffer tank by gravity through the guide pipe at the bottom of the dissolving kettle. It is then quantitatively pumped into the flash tank. The flash tank discharge is pumped into the crystallization tank by the transfer pump. The crystallization tank has a circulating water jacket and the temperature is controlled at 20-25℃. The dissolving liquid is cooled and crystallized in the crystallization tank. The crystallized aminosulfonic acid crystals flow into the thickener together with the mother liquor. The gas extracted from the flash tank is condensed by the condenser. The condensate enters the mother liquor tank and becomes the mother liquor. (7) The wet aminosulfonic acid product is dried at 50°C and vacuum degree below -0.09MPa for 6 hours to obtain high-purity aminosulfonic acid product. The gas gas coming out of the vacuum drying is condensed by a condenser, and the condensate enters the mother liquor tank to become the mother liquor.

[0023] Comparative Example 1 It is basically the same as Example 1, except that p-toluenesulfonic acid, sodium polyacrylate and hydroxyethylidene diphosphonic acid are not added.

[0024] Comparative Example 2 It is basically the same as Example 1, except that p-toluenesulfonic acid and sodium polyacrylate are not added.

[0025] Comparative Example 3 It is basically the same as Example 1, except that hydroxyethylidene diphosphonic acid is not added.

[0026] Comparative Example 4 It is basically the same as Example 1, except that p-toluenesulfonic acid is not added.

[0027] Comparative Example 5 It is basically the same as Example 1, except that sodium polyacrylate is not added.

[0028] The high-purity aminosulfonic acid finished product and its quality are measured according to the method of HG / T 2527-2011, as detailed in Table 1.

[0029] Table 1. Effects of different additives on the finished aminosulfonic acid product

[0030] As shown in Table 1, the aminosulfonic acid prepared by the method of the present invention not only has a high yield (88.2%), but also a high-quality finished product that meets the requirements for superior grade aminosulfonic acid. The principle behind this method is roughly as follows: The reaction stabilizer (p-toluenesulfonic acid) of this invention utilizes the electronic effect of its large π-conjugated system of aromatic ring to form a stable sulfonate anion in a strong acid environment. The sulfonate anion effectively shields the electron-rich center of the carbonyl oxygen in the urea molecule through electrostatic interaction, slows down the electrophilic attack rate of SO3 molecules on urea, and moderates the release rate of isocyanate intermediate, thereby inhibiting the polymerization side reaction caused by its instantaneous high concentration. The metal ion masking agent has a dual function: (1) In a strong acid environment, its phosphonate group still retains some coordination ability and can react with Fe 3+ Ca 2+ (1) When metal ions form soluble complexes, they remain in the liquid phase; (2) The -PO3 in their molecules 2- The group and the -SO3 group in the target product aminosulfonic acid molecule - The groups have similar tetrahedral spatial configurations and charge distributions, preferentially adsorbing at active sites or defects in crystal growth, forming spatial and electrical barriers that effectively prevent metal ions from migrating or embedding into the crystal lattice, thereby improving product purity. The crystallization process regulator (sodium polyacrylate), as an anionic or nonionic polymer, adsorbs onto the surface of aminosulfonic acid crystal nuclei in acidic media through functional groups such as carboxyl groups on its molecular chain. Through steric hindrance and electrostatic repulsion, it prevents the rapid aggregation and adhesion of tiny crystal nuclei, effectively reducing the inclusion of mother liquor in intergranular gaps and crystal defects, effectively lowering sulfate content, and improving product purity.

[0031] Examples 2-4 The results are basically the same as in Example 1, except that the amounts of p-toluenesulfonic acid, sodium polyacrylate, and hydroxyethylidene diphosphonic acid added are different, as shown in Table 2.

[0032] Table 2. Mass of aminosulfonic acid products prepared in different embodiments

[0033] As shown in Table 2, Example 2 produced a high-quality aminosulfonic acid product with the highest yield, even with a smaller amount of additives. Therefore, based on the process parameters of Example 2, 10 batches of repeatability tests were conducted, and the specific results are shown in Table 3.

[0034] Table 3. Stability test results of Example 2

[0035] As shown in Table 3, the yield of aminosulfonic acid prepared by the method of the present invention is 88.2%, and the aminosulfonic acid is a white crystal with a content of 99.7%.

[0036] This invention introduces a multifunctional composite additive consisting of a reaction stabilizer, a metal ion masking agent, and a crystallization regulator, in synergy with an optimized reaction-crystallization process. By first feeding at a low temperature and then using the heat of reaction to mature the mixture, the synthesis reaction is ensured to be stable and efficient. In the purification stage, a flash evaporation-assisted recrystallization technique is used, combined with dissolution and rapid crystallization using a specific concentration of dilute sulfuric acid, to efficiently separate impurities and obtain high-purity crystals.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-quality aminosulfonic acid from fuming sulfuric acid, characterized in that, Includes the following steps: (1) Dissolve the reaction stabilizer and metal ion masking agent in a solvent to prepare a first dispersion with a mass concentration of 10%-20%; dissolve the crystallization regulator in a solvent to prepare a second dispersion with a mass concentration of 3%-8%, for later use; (2) Add fuming sulfuric acid to the reaction vessel, then add the first dispersion, and stir at 70-80 rpm for 5-15 minutes; (3) Add urea to the reactor, control the rate of urea addition, maintain the material temperature ≤70℃, and use the heat of reaction to raise the material temperature in the reactor to 80-85℃ before the urea addition is nearing completion. After the urea is added, stir at 70-80 rpm for 5-10 minutes and keep warm for 1-2 hours. (4) After the reaction is completed, add the second dispersion to the reaction solution, cool down to 40-45℃, add solvent, maintain the material temperature ≤70℃, adjust the sulfuric acid content in the reactor to 70%, and after the addition is completed, cool down to 40-45℃ and carry out solid-liquid separation to obtain wet crude aminosulfonic acid and dilute acid with a concentration of 70%. The dilute acid is filtered after precipitation to become an industrial product. (5) The wet crude aminosulfonic acid product is rinsed with deionized water and / or mother liquor. The rinsing solution is then precipitated to become washing water. (6) Stir and heat dilute sulfuric acid and / or mother liquor to 40-45℃ at a speed of 70-80 rpm, add the washed crude aminosulfonic acid, and dissolve it into a transparent liquid under the condition that the material temperature is ≤70℃. Then flash evaporate the liquid. The flash evaporated condensate becomes the mother liquor. Cool the flash evaporated aminosulfonic acid solution to crystallize. The crystallized aminosulfonic acid crystals and liquid flow into a thickener for solid-liquid separation. The separated liquid becomes the mother liquor and the solid is aminosulfonic acid crystals. (7) The aminosulfonic acid crystals are vacuum dried to obtain high-purity aminosulfonic acid product. The gas produced by vacuum drying is condensed to obtain condensate, which becomes the mother liquor.

2. The method according to claim 1, characterized in that: The reaction stabilizer is p-toluenesulfonic acid or p-aminobenzenesulfonic acid, and the amount added is 0.2%-0.4% of the urea quality.

3. The method according to claim 1, characterized in that: The metal ion masking agent is one or more of hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, or diethylenetriaminepentamethylidene phosphonic acid, and its addition amount is 0.05%-0.1% of the urea quality.

4. The method according to claim 1, characterized in that: The crystallization regulator is sodium polyacrylate, and its addition amount is 0.01%-0.06% of the urea quality.

5. The method according to any one of claims 1-4, characterized in that: The mass concentration of free SO3 in the fuming sulfuric acid is 20%-30%.

6. The method according to claim 5, characterized in that: The mass ratio of urea to fuming sulfuric acid is 1:6.0-6.

4.

7. The method according to claim 1, characterized in that: The vacuum drying process specifically involves drying for 4-6 hours at 50-70°C and a vacuum level below -0.09 MPa.

8. The method according to claim 1, characterized in that: The solvent is deionized water and / or washing water.

9. The method according to claim 1, characterized in that: The dilute sulfuric acid mentioned is a sulfuric acid solution with a concentration of 5-30%.

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