Production method of monoammonium phosphate

Abstract

The invention belongs to the technical field of chemical fertilizers, and provides a production method of monoammonium phosphate. The production method comprises the following steps: (1) hydrolyzing sodium pyrophosphate in raw material acid to obtain sodium dihydrogen phosphate; the raw material acid is hot-process phosphoric acid or wet-process purified acid; (2) dissolving sodium dihydrogen phosphate and ammonium bicarbonate in water, reacting in a reaction kettle at the temperature of 25-30 DEG C for 2-3 hours, and filtering to obtain a sodium bicarbonate solid and filtrate; and (3) adjusting the pH value of the filtrate to 4.0-4.4, reacting at 60-70 DEG C for 2-3 hours, concentrating until the specific gravity is 1.2-1.6, cooling, crystallizing, centrifuging and drying to obtain monoammonium phosphate and mother liquor. According to the production method, sodium pyrophosphate is used as a raw material to produce monoammonium phosphate and sodium bicarbonate at the same time, the raw material source of monoammonium phosphate can be widened, diversified utilization of the raw material is achieved, economic benefits and environmental friendliness of the production process can be improved through high-value utilization of by-products, and the method is suitable for industrial production. The method has important significance for promoting the sustainable development of the phosphorus chemical industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical fertilizers, and in particular relates to a method for producing monoammonium phosphate. Background Art

[0002] Monoammonium phosphate (MAP, molecular formula NH4H2PO4) is an important high-concentration water-soluble phosphate compound fertilizer, widely used in agricultural production, especially in integrated water-fertilizer systems such as drip irrigation and sprinkler irrigation. Due to its high phosphorus content and good water solubility, it can provide efficient phosphorus and nitrogen nutrition for crops, significantly improving crop yield and quality. At the same time, in the industrial field, monoammonium phosphate is also used as a fire retardant for wood, paper, and fabrics, and as a dry powder fire extinguishing agent.

[0003] Traditional monoammonium phosphate (MAP) production methods primarily use phosphate rock as a raw material, reacting it with sulfuric acid to produce phosphoric acid, which is then neutralized with liquid ammonia. However, this process suffers from high energy consumption, harsh reaction conditions, and the need to process large amounts of waste residue, such as phosphogypsum. This not only increases production costs but also imposes a serious environmental burden. Furthermore, phosphate rock is a non-renewable resource, and long-term reliance on this raw material faces the risk of resource depletion. In recent years, technologies for preparing MAP using industrial by-products or waste as raw materials have gradually gained attention, aiming to reduce dependence on phosphate rock and achieve resource recycling. However, most of these methods have disadvantages such as complex process flows, low product purity, and difficulty in achieving large-scale production, which limit their industrial application.

[0004] Sodium pyrophosphate (Na4P2O7) is a common inorganic phosphate widely used in food additives, detergents, water treatment agents, and other fields. Its production process is mature and the market supply is sufficient. Currently, the main products produced domestically using sodium pyrophosphate as a raw material include trisodium phosphate, disodium phosphate, monosodium phosphate, sodium tripolyphosphate, and potassium dihydrogen phosphate. However, these products are currently experiencing weak market sales, making it difficult for companies to make a profit. In particular, the production of potassium dihydrogen phosphate produces a large amount of sodium chloride waste salt as a by-product, which is currently difficult to process and poses a significant environmental pressure.

[0005] As an industrial-grade product, sodium bicarbonate (NaHCO3) has a wide range of application needs in food processing, medicine, fire protection and other industries.

[0006] At present, there is no report on a mature production process for simultaneously preparing fully water-soluble fertilizer-grade monoammonium phosphate and industrial-grade sodium bicarbonate as a by-product using sodium pyrophosphate as a raw material. Summary of the Invention

[0007] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for producing monoammonium phosphate, which uses sodium pyrophosphate as a raw material to simultaneously produce monoammonium phosphate and sodium bicarbonate. This production method can not only broaden the raw material sources of monoammonium phosphate and realize the diversified utilization of raw materials, but also improve the economic benefits and environmental friendliness of the production process through the high-value utilization of by-products, which is of great significance for promoting the sustainable development of the phosphorus chemical industry.

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

[0009] A method for producing monoammonium phosphate comprises: (1) hydrolyzing sodium pyrophosphate in a raw acid to obtain sodium dihydrogen phosphate; the raw acid is thermal phosphoric acid or wet purified acid; (2) dissolving sodium dihydrogen phosphate and ammonium bicarbonate in water at a molar ratio of 1:2, reacting in a reactor at a temperature of 25-30°C for 2-3 hours, filtering to obtain sodium bicarbonate solid and a filtrate; (3) adjusting the pH of the filtrate to 4.0-4.4, reacting at 60-70°C for 2-3 hours, concentrating to a specific gravity of 1.2-1.6, cooling, crystallizing, centrifuging, and drying to obtain monoammonium phosphate and a mother liquor.

[0010] Furthermore, in a preferred embodiment of the present invention, in step (3), raw acid is added to adjust the pH of the filtrate.

[0011] Furthermore, in a preferred embodiment of the present invention, the preparation of wet-process purified acid comprises: adding an impurity remover to wet-process phosphoric acid, reacting at 60-70° C. for 2 hours, and filtering to obtain the wet-process purified acid.

[0012] Furthermore, in a preferred embodiment of the present invention, the content of P2O5 in the raw acid is 40%.

[0013] Furthermore, in a preferred embodiment of the present invention, the impurity remover includes sodium sulfide and food-grade diatomaceous earth.

[0014] Furthermore, in a preferred embodiment of the present invention, the mass ratio of wet-process phosphoric acid, sodium sulfide and food-grade diatomaceous earth is 1:0.005:0.005.

[0015] Furthermore, in a preferred embodiment of the present invention, in step (1), the conditions for hydrolyzing sodium pyrophosphate include: mixing sodium pyrophosphate and raw acid according to 4-6 g; 100 mL to obtain a sodium pyrophosphate solution, heating the sodium pyrophosphate solution on an electric furnace to boiling, maintaining a slight boil for 5 minutes, cooling and filtering to obtain sodium dihydrogen phosphate.

[0016] The beneficial effects of the production method of monoammonium phosphate provided by the present invention are:

[0017] (1) The production method of monoammonium phosphate provided by the present invention can achieve diversified and efficient utilization of raw materials, breaking through the traditional dependence of monoammonium phosphate production on a single raw material such as phosphate rock, and innovatively using sodium pyrophosphate as the starting raw material. The hydrolysis process of sodium pyrophosphate converts polymeric phosphorus into a reactive phosphorus form. The hydrolysis product fully reacts with ammonium bicarbonate, allowing the efficient utilization of phosphorus. This broadens the raw material source for monoammonium phosphate production, improves the comprehensive utilization rate of phosphorus resources, achieves diversified utilization of raw materials, and opens up a new raw material path for the phosphorus chemical industry.

[0018] (2) The production method of monoammonium phosphate provided by the present invention can achieve high-value utilization of by-products and improve economic benefits. Sodium bicarbonate is generated simultaneously during the production process. By separating and purifying the by-product sodium bicarbonate, high-value utilization of the by-product is achieved, which not only reduces production costs but also creates additional economic benefits. The entire production process forms a virtuous cycle of synergistic value-added between raw materials and by-products, significantly improving the economic benefits of the production process.

[0019] (3) The production method of monoammonium phosphate provided by the present invention significantly enhances environmental friendliness: the process achieves the exchange of sodium ions and ammonium ions through a double decomposition reaction, ultimately obtaining monoammonium phosphate and sodium bicarbonate products, with a product yield of ≥95%. This fundamentally solves the market and environmental issues of waste salt sodium chloride for production enterprises. The high-value utilization of by-products avoids the generation of waste and reduces environmental pollution, conforming to the concepts of green chemistry and sustainable development, improving the environmental friendliness of the production process, and helping to reduce the environmental burden of the phosphorus chemical industry.

[0020] The monoammonium phosphate production method provided by the present invention provides a new, efficient and green production model for the phosphorus chemical industry through raw material innovation, by-product utilization and environmental optimization. It is of great significance for promoting technological upgrading and sustainable development of the phosphorus chemical industry, helping to enhance the overall competitiveness of the industry and promote the green transformation and high-quality development of the phosphorus chemical industry. DETAILED DESCRIPTION

[0021] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0022] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0023] Example 1

[0024] This embodiment provides a method for producing monoammonium phosphate, comprising: (1) mixing sodium pyrophosphate and wet-process purified acid having a P2O5 content of 40% in 5 g / 100 mL amounts, and filtering to obtain sodium dihydrogen phosphate; (2) dissolving sodium dihydrogen phosphate and ammonium bicarbonate in water in a molar ratio of 1:2, reacting the mixture in a reactor at a temperature of 28° C. for 2.5 hours, filtering to obtain sodium bicarbonate solid and a filtrate; and (3) adding wet-process purified acid having a P2O5 content of 40% to adjust the pH of the filtrate to 4.2, reacting the mixture at 65° C. for 2.5 hours, concentrating the mixture to a specific gravity of 1.25, cooling, crystallizing, centrifuging, and drying to obtain monoammonium phosphate.

[0025] Example 2

[0026] This embodiment provides a method for producing monoammonium phosphate, comprising: (1) mixing sodium pyrophosphate and wet-process purified acid with a P2O5 content of 40% in an amount of 4 g / 100 mL to obtain a sodium pyrophosphate solution, and filtering to obtain sodium dihydrogen phosphate; (2) dissolving sodium dihydrogen phosphate and ammonium bicarbonate in water in a molar ratio of 1:2, reacting the mixture in a reactor at a temperature of 25° C. for 3 hours, filtering to obtain sodium bicarbonate solid and a filtrate; and (3) adding wet-process phosphoric acid with a P2O5 content of 40% to adjust the pH of the filtrate to 4.0, reacting the mixture at 60° C. for 3 hours, concentrating the mixture to a specific gravity of 1.2, cooling, crystallizing, centrifuging, and drying to obtain monoammonium phosphate.

[0027] Example 3

[0028] This embodiment provides a method for producing monoammonium phosphate, comprising: (1) mixing sodium pyrophosphate and wet-process purified acid with a P2O5 content of 40% in an amount of 6 g to 100 mL to obtain a sodium pyrophosphate solution, and filtering to obtain sodium dihydrogen phosphate; (2) dissolving sodium dihydrogen phosphate and ammonium bicarbonate in water in a molar ratio of 1:2, reacting the mixture in a reactor at a temperature of 30° C. for 2 h, filtering to obtain sodium bicarbonate solid and a filtrate; (3) adding wet-process phosphoric acid with a P2O5 content of 40% to adjust the pH of the filtrate to 4.4, reacting the mixture at 70° C. for 2 h, concentrating the mixture to a specific gravity of 1.6, cooling, crystallizing, centrifuging, and drying to obtain monoammonium phosphate.

[0029] Example 4

[0030] This embodiment provides a method for producing monoammonium phosphate, which differs from Example 1 in that: step (3): wet-process purified acid having a P2O5 content of 40% is added to adjust the pH of the filtrate, and the preparation of the wet-process purified acid comprises: adding sodium sulfide and food-grade diatomaceous earth to wet-process phosphoric acid in a mass ratio of 1:0.005:0.005, reacting at 65°C for 2h, and filtering to obtain the wet-process purified acid.

[0031] Example 5

[0032] This embodiment provides a method for producing monoammonium phosphate, which differs from Example 4 in that step (1) further comprises: placing a sodium pyrophosphate solution on an electric furnace and heating it to boiling, maintaining a slight boiling for 5 minutes, cooling it, and filtering it to obtain sodium dihydrogen phosphate.

[0033] Example 6

[0034] This embodiment provides a method for producing monoammonium phosphate, which differs from Example 5 in that the wet-process purified acid with a P2O5 content of 40% is replaced by thermal phosphoric acid with a P2O5 content of 40%.

[0035] Comparative Example 1

[0036] This comparative example provides a method for producing monoammonium phosphate, comprising: (1) mixing sodium pyrophosphate and wet-process purified acid with a P2O5 content of 50% in 10 g and 100 mL, filtering to obtain sodium dihydrogen phosphate; (2) dissolving sodium dihydrogen phosphate and ammonium bicarbonate in water in a molar ratio of 1:3, reacting in a reactor at a temperature of 35° C. for 2 h, filtering to obtain sodium bicarbonate solid and a filtrate; (3) adding wet-process purified acid with a P2O5 content of 50% to adjust the pH of the filtrate to 3.8, reacting at 75° C. for 1.5 h, concentrating to a specific gravity of 1.25, cooling, crystallizing, centrifuging, and drying to obtain monoammonium phosphate.

[0037] Comparative Example 2

[0038] This comparative example provides a method for producing monoammonium phosphate, which differs from Example 4 in that: step (3): wet-process purified acid having a P2O5 content of 40% is added to adjust the pH of the filtrate, and the preparation of the wet-process purified acid comprises: adding sodium sulfide to wet-process phosphoric acid at a mass ratio of 1:0.001, reacting at 65°C for 2h, and filtering to obtain the wet-process purified acid.

[0039] Comparative Example 3

[0040] This comparative example provides a method for producing monoammonium phosphate, which differs from Example 4 in that: step (3): wet-process purified acid having a P2O5 content of 40% is added to adjust the pH of the filtrate, and the preparation of the wet-process purified acid comprises: adding food-grade diatomaceous earth to wet-process phosphoric acid in a mass ratio of 1:0.001, reacting at 65°C for 2h, and filtering to obtain the wet-process purified acid.

[0041] Experimental Example 1

[0042] Experimental method: The yields of sodium bicarbonate and monoammonium phosphate obtained in Examples 1-6 and Comparative Examples 1-3 were calculated as follows:

[0043] 1. Key chemical reaction equations

[0044] (1) Sodium pyrophosphate is hydrolyzed in the raw acid to form sodium dihydrogen phosphate:

[0045] Na4P2O7+2H3PO4+H2O→4NaH2PO4

[0046] (2) Sodium dihydrogen phosphate reacts with ammonium bicarbonate and diammonium hydrogen phosphate and sodium bicarbonate:

[0047] NaH2PO4+2NH4HCO3→(NH4)2HPO4+NaHCO3+H2O+CO2↑

[0048] (3) Reaction of diammonium hydrogen phosphate with wet-process phosphoric acid

[0049] (NH4)2HPO4+H3PO4→2NH4H2PO4

[0050] 2. Calculation of sodium bicarbonate (NaHCO3) yield

[0051] Theoretical yield calculation: Based on sodium pyrophosphate (Na4P2O7), assuming the input amount is m sodium pyrophosphate (kg), the molar mass is 265.9 g / mol, then the amount of substance is: n 焦磷酸钠 =m 焦磷酸钠 ×1000 / 265.9;

[0052] According to reaction formulas (1) and (2), 1 mol of sodium pyrophosphate will eventually generate 2×2=4 mol of NaHCO3, so the theoretical yield is: m NaHCO3理论 =n 焦磷酸钠 ×4×84.01 g / mol÷1000 (kg) (NaHCO3 molar mass: 84.01 g / mol).

[0053] Calculation of actual yield: The mass of NaHCO3 obtained after separation and drying is m NaHCO3实际 (kg).

[0054] Yield formula: NaHCO3 yield = m NaHCO3实际 / m NaHCO3理论 ×100%

[0055] 3.3. Calculation of Monoammonium Phosphate (NH4H2PO4) Yield

[0056] Theoretical yield calculation: Also based on sodium pyrophosphate, 1 mol of sodium pyrophosphate generates 2 mol of (NH4)2HPO4 through reactions (1) and (2), and then reacts with phosphoric acid to generate 4 mol of NH4H2PO4;

[0057] Theoretical output: m 磷酸一铵理论 =n 焦磷酸钠×4×115.03 g / mol÷1000 (kg) (NH4H2PO4 molar mass: 115.03 g / mol).

[0058] Actual yield: The mass of monoammonium phosphate obtained after separation and drying is: m 磷酸一铵实际 (kg).

[0059] Yield formula: monoammonium phosphate yield = m 磷酸一铵实际 / m 磷酸一铵理论 ×100%.

[0060] The yields (%) of sodium bicarbonate and monoammonium phosphate obtained in Examples 1-6 and Comparative Examples 1-3 are shown in Table 1:

[0061] Table 1

[0062]

[0063]

[0064] As can be seen from the data in Table 1, Examples 1-6 of the present application achieve the exchange of sodium ions and ammonium ions through a double decomposition reaction, ultimately obtaining ammonium dihydrogen phosphate and sodium bicarbonate products, and the yield of the product is ≥95%, which can fundamentally solve the market problems of the production enterprise and the environmental protection problems of waste salt sodium chloride.

[0065] Example 2

[0066] After testing, the monoammonium phosphate obtained in Examples 1-6 meets the requirements of key indicators such as fertilizer-grade nutrients, moisture, particle size, and heavy metals in the national standard GB / T 10205-2022 "Monoammonium Phosphate and Diammonium Phosphate", and can be judged to be fertilizer-grade monoammonium phosphate.

[0067] After testing, the sodium bicarbonate obtained in Examples 1-6 meets the requirements of key indicators such as industrial-grade chloride, moisture, slurry and insoluble matter in the national standard GB / T 1606-2019 "Industrial Sodium Bicarbonate", and can be judged to be industrial-grade sodium bicarbonate.

[0068] In summary, the production method of monoammonium phosphate provided by the present invention uses sodium pyrophosphate as a raw material to simultaneously produce monoammonium phosphate and sodium bicarbonate. This production method can not only broaden the raw material source of monoammonium phosphate and realize the diversified utilization of raw materials, but also improve the economic benefits and environmental friendliness of the production process through the high-value utilization of by-products, which is of great significance for promoting the sustainable development of the phosphorus chemical industry.

[0069] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for producing monoammonium phosphate, characterized in that: include: (1) hydrolyzing sodium pyrophosphate in a raw acid to obtain sodium dihydrogen phosphate; the raw acid is thermal phosphoric acid or wet purified acid; (2) dissolving the sodium dihydrogen phosphate and ammonium bicarbonate in water at a molar ratio of 1:2, reacting in a reactor at a temperature of 25-30° C. for 2-3 hours, filtering to obtain sodium bicarbonate solid and a filtrate; (3) adjusting the pH of the filtrate to 4.0-4.4, reacting at 60-70° C. for 2-3 hours, concentrating to a specific gravity of 1.2-1.6, and then cooling, crystallizing, centrifuging, and drying to obtain the monoammonium phosphate.

2. The method for producing monoammonium phosphate according to claim 1, wherein: In step (3), the raw acid is added to adjust the pH of the filtrate.

3. The method for producing monoammonium phosphate according to claim 1, wherein: The preparation of the wet-process purified acid comprises: adding an impurity remover to wet-process phosphoric acid, reacting at 60-70° C. for 2 hours, and filtering to obtain the wet-process purified acid.

4. The method for producing monoammonium phosphate according to claim 1, wherein: The content of P2O5 in the raw acid is 40%.

5. The method for producing monoammonium phosphate according to claim 4, wherein: The impurity remover includes sodium sulfide and food grade diatomaceous earth.

6. The method for producing monoammonium phosphate according to claim 5, wherein: The mass ratio of the wet-process phosphoric acid, the sodium sulfide and the food-grade diatomaceous earth is 1:0.005:0.

005.

7. The method for producing monoammonium phosphate according to claim 1, wherein: In step (1), the conditions for hydrolyzing the sodium pyrophosphate include: mixing the sodium pyrophosphate and the raw acid according to 4-6 g / 100 mL to obtain a sodium pyrophosphate solution, heating the sodium pyrophosphate solution on an electric furnace to boiling, maintaining a slight boil for 5 minutes, cooling, and filtering to obtain the sodium dihydrogen phosphate.

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