A method for preparing industrial grade potassium dihydrogen phosphate by means of metathetic extraction

Abstract

This invention relates to a method for preparing industrial-grade potassium dihydrogen phosphate using a metathesis extraction method, belonging to the technical field of fine chemicals. This invention utilizes phosphate, potassium salt, and sulfuric acid raw materials to produce potassium dihydrogen phosphate through a metathesis and extraction process. In the process of this invention, the generated potassium dihydrogen phosphate dissolves in the aqueous phase, while the generated calcium sulfate dihydrate precipitates; these two can be separated using a simple solid-liquid separation method. The small amount of hydrochloric acid contained in the filtrate can be separated by extraction, yielding high-quality industrial-grade potassium dihydrogen phosphate while simultaneously producing ammonium chloride as a byproduct. The preparation method of this invention has advantages in terms of cost and product quality, the process is easy to implement, and the extractant can be recovered and reused.

Description

Technical Field

[0001] This invention relates to the technical field of fine chemicals, specifically to a method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction. Background Technology

[0002] Potassium dihydrogen phosphate (KH2PO4) has a wide range of applications in the food, industrial, and livestock sectors. Currently, there are several production processes for KH2PO4, including neutralization, metathesis, solvent extraction, direct extraction, ion exchange, and electrolysis. Among these, the neutralization method offers advantages such as simplicity and high product quality. Currently, 90% of industrial-grade KH2PO4 is produced using this method. This method uses high-quality industrial-grade phosphoric acid and industrial-grade potassium hydroxide as raw materials. However, the raw material is industrial-grade phosphoric acid. Whether using the thermal or wet process, the production cost is relatively high, and the quality of KH2PO4 produced using the thermal process is higher than that produced using the wet process.

[0003] However, the thermal process for producing phosphoric acid is characterized by high energy consumption and pollution, and is gradually being replaced by the wet process. However, the wet process produces a wider variety of impurity ions, with higher levels of some metal ions. Using the wet process to produce industrial-grade potassium dihydrogen phosphate presents challenges in controlling process parameters and ensuring inconsistent product quality. Other methods for producing potassium dihydrogen phosphate also have their own problems and have not been widely adopted. For example, the single extraction method for producing potassium dihydrogen phosphate suffers from poor separation efficiency, high extraction costs, and difficulties in recovering and reusing the extractant. The ion exchange method is currently immature, lacks operability, and is still in the exploratory stage.

[0004] The above methods for producing potassium dihydrogen phosphate all suffer from problems such as high cost, high impurity content, low product purity, and unstable quality. There is an urgent need to find a low-cost, low-energy-consumption potassium dihydrogen phosphate production process with high product quality. Summary of the Invention

[0005] To address the problems of high phosphate rock grade requirements, high energy consumption, and relatively high costs associated with existing neutralization methods for producing potassium dihydrogen phosphate, this invention provides a method for preparing industrial-grade potassium dihydrogen phosphate using a metathesis extraction method. This invention utilizes phosphate, potassium salt, and sulfuric acid raw materials through a metathesis and extraction process to produce potassium dihydrogen phosphate, offering advantages in both cost and product quality. It is also easier to implement, and the extractant can be recycled and reused, further reducing production costs.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction includes the following steps:

[0008] (1) Potassium chloride is fed into the reactor, then calcium phosphate is added to the reactor, and then 98% sulfuric acid solution is added to the reactor at a specified rate using a peristaltic pump; during the reaction, hydrogen chloride is extracted, the pH of the reaction system is maintained at 4.2~4.5, the reaction temperature is 55~65℃, and the reaction time is 60min-90min; the reaction formula is as follows:

[0009] Ca3(PO4)2+3H2SO4+2KCl+6H2O=3CaSO4·2H2O+2KH2PO4+2HCl;

[0010] (2) The material obtained in step (1) is filtered while hot. The filter residue is phosphogypsum and the filtrate is a potassium dihydrogen phosphate solution containing hydrochloric acid.

[0011] (3) Extract the potassium dihydrogen phosphate solution containing hydrochloric acid in step (2) with an extractant. The oil-to-water ratio of the extractant phase is 3-9:1, and the organic phase and aqueous phase are obtained respectively. The main component of the aqueous phase is potassium dihydrogen phosphate.

[0012] The extractant consists of three components: A, B, and C. Component A is trioctylamine or triethylamine; component B is trioctyldecyl tertiary amine or di-2-ethylhexyl phosphate; and component C is dodecane or kerosene.

[0013] (4) The aqueous phase obtained in step (3) is concentrated and the temperature is controlled at 165~175℃. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40~50℃ to obtain potassium dihydrogen phosphate slurry. The potassium dihydrogen phosphate wet product is obtained by centrifugation and the mother liquor is returned to the reactor. The wet product is dried to finally obtain potassium dihydrogen phosphate product.

[0014] Furthermore, in step (3), the extraction temperature is 25~60℃, the extraction time is 15~30min, and the stirring speed is 150~300r / min.

[0015] Furthermore, in step (1), the potassium chloride contains 58% to 62% potassium oxide, and the calcium phosphate contains 35% to 41% phosphorus pentoxide.

[0016] Furthermore, the 98% sulfuric acid solution is pumped into the reaction system at a rate of 30-50 ml / min.

[0017] Furthermore, the volume ratio of components A, B, and C is 3~8:3~8:2~4.

[0018] Furthermore, in step (4), the cooling rate of the concentrated potassium dihydrogen phosphate filtrate is 0.2~0.8℃ / min.

[0019] Furthermore, in step (3), the organic phase of extraction is back-extracted with 25%~28% ammonia water, the aqueous phase after back-extraction is ammonium chloride solution, and the organic phase is the regenerated extractant; the oil-water ratio (O / A) of the back-extraction phase is 4~9:1, the back-extraction temperature is 25~65℃, the back-extraction time is 15~30min, and the stirring speed is 150~300r / min.

[0020] Furthermore, the hydrogen chloride generated in step (1) is adsorbed with ammonia water to obtain an ammonium chloride solution; then it is combined with the back-extracted water and concentrated, with the temperature controlled at 70~80℃. After concentration, cooling and crystallization, the solid and liquid are separated to obtain ammonium chloride.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) Compared with the prior art, the present invention replaces the traditional production process using phosphoric acid and potassium hydroxide as raw materials. It uses phosphate, potassium salt and sulfuric acid raw materials to produce potassium dihydrogen phosphate products through metathesis and extraction processes, which has more advantages in cost and product quality. The process is easy to implement, and the extractant can be recycled and reused.

[0023] (2) In the process of the present invention, the generated potassium dihydrogen phosphate dissolves in the aqueous phase during the reaction, and the generated calcium sulfate dihydrate is a precipitate. The two can be separated by a simple solid-liquid separation method. The small amount of hydrochloric acid contained in the filtrate can be separated by extraction, and ammonium chloride is produced as a byproduct while obtaining high-quality industrial-grade potassium dihydrogen phosphate. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart illustrating the preparation process according to an embodiment of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0027] Example 1

[0028] A method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction includes the following steps:

[0029] (1) Weigh 200g of potassium chloride with a potassium oxide content of 60% and put it into the reactor. Then add 477.03g of calcium phosphate with a phosphorus pentoxide content of 38% into the reactor. Then add 98% sulfuric acid solution into the reactor at a rate of 35ml / min using a peristaltic pump. Extract hydrogen chloride gas using a vacuum pump and control the vacuum degree at 0.087Mpa. Absorb the hydrogen chloride gas with ammonia water to obtain a dilute ammonium chloride solution. Maintain the pH of the reaction system at 4.2, the reaction temperature at 55℃, and the reaction time at 60min.

[0030] (2) The material obtained in step (1) is filtered while hot. The filter residue is phosphogypsum and the filtrate is a potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid.

[0031] (3) The potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid in step (2) was extracted with an extractant at an extraction temperature of 25°C, an oil-to-water ratio (O / A) of 3:1, an extraction time of 15 min, and a stirring speed of 150 r / min to obtain an organic phase and an aqueous phase respectively; the main component of the aqueous phase was potassium dihydrogen phosphate.

[0032] The extractant consists of trioctylamine, trioctyldecyl tertiary amine and dodecane in a volume ratio of 3:3:2.

[0033] (4) The aqueous phase obtained in step (3) is concentrated at a temperature of 165°C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40°C at a cooling rate of 0.2°C / min to obtain potassium dihydrogen phosphate slurry. The wet potassium dihydrogen phosphate product is obtained by centrifugation, and the mother liquor is returned to the reactor. The wet product is dried to obtain the potassium dihydrogen phosphate product. See Table 1 for detailed test data of potassium dihydrogen phosphate product.

[0034] (5) The organic phase from step (3) was back-extracted with 27% ammonia water. The oil-to-water ratio (O / A) of the back-extracted phase was 4:1, the back-extraction temperature was 25℃, the back-extraction time was 15 min, and the stirring speed was 150 r / min. The aqueous phase after back-extraction was an ammonium chloride solution, and the organic phase was used as the regenerated extractant, which was returned to the extraction system for reuse. The aqueous phase and the dilute ammonium chloride solution absorbed by ammonia water in the metathesis step were combined and concentrated at a controlled temperature of 70℃. After concentration, cooling, and crystallization, the ammonium chloride byproduct was obtained by centrifugation. The ammonium chloride detection data are detailed in Table 2.

[0035] Example 2

[0036] A method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction includes the following steps:

[0037] (1) Weigh 300g of potassium chloride with a potassium oxide content of 60% and put it into the reactor. Then add 679.81g of calcium phosphate with a phosphorus pentoxide content of 40% into the reactor. Then add 98% sulfuric acid solution into the reactor at a rate of 45ml / min using a peristaltic pump. Extract hydrogen chloride gas using a vacuum pump and control the vacuum degree at 0.090Mpa. Absorb the hydrogen chloride gas with ammonia water to obtain a dilute ammonium chloride solution. Maintain the pH of the reaction system at 4.3, the reaction temperature at 60℃, and the reaction time at 75min.

[0038] (2) The material obtained in step (1) is filtered while hot. The filter residue is phosphogypsum and the filtrate is a potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid.

[0039] (3) The potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid in step (2) was extracted with an extractant at an extraction temperature of 35°C, an oil-to-water ratio (O / A) of 5:1, an extraction time of 20 min, and a stirring speed of 200 r / min to obtain an organic phase and an aqueous phase respectively; the main component of the aqueous phase was potassium dihydrogen phosphate.

[0040] The extractant consists of triethylamine, di-2-ethylhexyl phosphate and kerosene in a volume ratio of 5:5:3.

[0041] (4) The aqueous phase obtained in step (3) is concentrated at a temperature of 170°C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40°C at a cooling rate of 0.2°C / min to obtain potassium dihydrogen phosphate slurry. The potassium dihydrogen phosphate wet product is obtained by centrifugation, and the mother liquor is returned to the reactor. The wet product is dried to obtain potassium dihydrogen phosphate product. See Table 1 for detailed test data of potassium dihydrogen phosphate product.

[0042] (5) The organic phase from step (3) was back-extracted with 26% ammonia water. The oil-to-water ratio (O / A) of the back-extracted phase was 6:1, the back-extraction temperature was 35℃, the back-extraction time was 20 min, and the stirring speed was 200 r / min. The aqueous phase after back-extraction was an ammonium chloride solution, and the organic phase was used as the regenerated extractant, which was returned to the extraction system for reuse. The aqueous phase and the dilute ammonium chloride solution absorbed by ammonia water in the metathesis step were combined and concentrated at a controlled temperature of 70℃. After concentration, cooling, and crystallization, the ammonium chloride byproduct was obtained by centrifugation. The ammonium chloride detection data are detailed in Table 2.

[0043] Example 3

[0044] A method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction includes the following steps:

[0045] (1) Weigh 250g of potassium chloride with a potassium oxide content of 59% and put it into the reactor. Then add 571.34g of calcium phosphate with a phosphorus pentoxide content of 39% into the reactor. Then add 98% sulfuric acid solution into the reactor at a rate of 48ml / min using a peristaltic pump. Extract hydrogen chloride gas using a vacuum pump and control the vacuum degree at 0.093Mpa. Absorb the hydrogen chloride gas with ammonia water to obtain a dilute ammonium chloride solution. Maintain the pH of the reaction system at 4.4, the reaction temperature at 65℃, and the reaction time at 90min.

[0046] (2) The material obtained in step (1) is filtered while hot. The filter residue is phosphogypsum and the filtrate is a potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid.

[0047] (3) The potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid in step (2) was extracted with an extractant at an extraction temperature of 45°C, an oil-to-water ratio (O / A) of 7:1, an extraction time of 25 min, and a stirring speed of 300 r / min to obtain an organic phase and an aqueous phase respectively; the main component of the aqueous phase was potassium dihydrogen phosphate.

[0048] The extractant consists of triethylamine, trioctyldecyl tertiary amine and dodecane in a volume ratio of 5:6:3.

[0049] (4) The aqueous phase obtained in step (3) is concentrated at a temperature of 170°C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40°C at a cooling rate of 0.3°C / min to obtain potassium dihydrogen phosphate slurry. The potassium dihydrogen phosphate wet product is obtained by centrifugation, and the mother liquor is returned to the reactor. The wet product is dried to obtain potassium dihydrogen phosphate product. See Table 1 for detailed test data of potassium dihydrogen phosphate product.

[0050] (5) The organic phase from step (3) was back-extracted with 26% ammonia water. The oil-to-water ratio (O / A) of the back-extracted phase was 6:1, the back-extraction temperature was 35℃, the back-extraction time was 25 min, and the stirring speed was 300 r / min. The aqueous phase after back-extraction was an ammonium chloride solution, and the organic phase was used as the regenerated extractant, which was returned to the extraction system for reuse. The aqueous phase and the dilute ammonium chloride solution absorbed by ammonia water in the metathesis step were combined and concentrated at a controlled temperature of 75℃. After concentration, cooling, and crystallization, the ammonium chloride byproduct was obtained by centrifugation. The ammonium chloride detection data are detailed in Table 2.

[0051] Example 4

[0052] A method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction includes the following steps:

[0053] (1) Weigh 200g of potassium chloride with a potassium oxide content of 58% and put it into the reactor. Then add 461.13g of calcium phosphate with a phosphorus pentoxide content of 38% into the reactor. Then add 98% sulfuric acid solution into the reactor at a rate of 43ml / min using a peristaltic pump. Extract hydrogen chloride gas using a vacuum pump and control the vacuum degree at 0.090Mpa. Absorb the hydrogen chloride gas with ammonia water to obtain a dilute ammonium chloride solution. Maintain the pH of the reaction system at 4.5, the reaction temperature at 60℃, and the reaction time at 80min.

[0054] (2) The material obtained in step (1) is filtered while hot. The filter residue is phosphogypsum and the filtrate is a potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid.

[0055] (3) Extract the potassium dihydrogen phosphate solution containing a small amount of hydrochloric acid in step (2) with an extractant. The extraction temperature is 30℃, the oil-to-water ratio (O / A) of the extractant phase is 5:1, the extraction time is 30 min, and the stirring speed is 250 r / min. The organic phase and the aqueous phase are obtained respectively. The main component of the aqueous phase is potassium dihydrogen phosphate.

[0056] The extractant consists of trioctylamine, trioctyldecyl tertiary amine and kerosene in a volume ratio of 6:7:4.

[0057] (4) The aqueous phase obtained in step (3) is concentrated at a temperature of 170°C. The concentrated potassium dihydrogen phosphate filtrate is cooled to 45°C at a cooling rate of 0.5°C / min to obtain potassium dihydrogen phosphate slurry. The potassium dihydrogen phosphate wet product is obtained by centrifugation, and the mother liquor is returned to the reactor. The wet product is dried to obtain potassium dihydrogen phosphate product. See Table 1 for detailed test data of potassium dihydrogen phosphate product.

[0058] (5) The organic phase from step (3) was back-extracted with 28% ammonia water. The oil-to-water ratio (O / A) of the back-extracted phase was 8:1, the back-extraction temperature was 30℃, the back-extraction time was 30 min, and the stirring speed was 250 r / min. The aqueous phase after back-extraction was an ammonium chloride solution, and the organic phase was used as the regenerated extractant, which was returned to the extraction system for reuse. The aqueous phase and the dilute ammonium chloride solution absorbed by ammonia water in the metathesis step were combined and concentrated at a controlled temperature of 75℃. After concentration, cooling, and crystallization, the ammonium chloride byproduct was obtained by centrifugation. The ammonium chloride detection data are detailed in Table 2.

[0059] Test case

[0060] The potassium dihydrogen phosphate products prepared in Examples 1-4 were tested, and the specific results are shown in Table 1 below:

[0061] Table 1 - Detection results of potassium dihydrogen phosphate

[0062]

[0063] The ammonium chloride byproducts prepared in Examples 1-4 were tested, and the specific results are shown in Table 2 below:

[0064] Table 2 - Ammonium chloride detection results

[0065]

[0066] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction, characterized in that, Includes the following steps: (1) Potassium chloride is fed into the reactor, then calcium phosphate is added to the reactor, and then 98% sulfuric acid solution is added to the reactor at a specified rate using a peristaltic pump; hydrogen chloride is extracted during the reaction, the pH of the reaction system is maintained at 4.2~4.5, the reaction temperature is 55~65℃, and the reaction time is 60min-90min; (2) The material obtained in step (1) is filtered while hot. The filter residue is phosphogypsum and the filtrate is potassium dihydrogen phosphate solution containing hydrochloric acid. (3) Extract the potassium dihydrogen phosphate solution containing hydrochloric acid in step (2) with an extractant. The oil-to-water ratio of the extractant phase is 3-9:1, and the organic phase and aqueous phase are obtained respectively. The main component of the aqueous phase is potassium dihydrogen phosphate. The extractant consists of three components: A, B, and C. Component A is trioctylamine or triethylamine; component B is trioctyldecyl tertiary amine or di-2-ethylhexyl phosphate; and component C is dodecane or kerosene. (4) The aqueous phase obtained in step (3) is concentrated and the temperature is controlled at 165~175℃. The concentrated potassium dihydrogen phosphate filtrate is cooled to 40~50℃ to obtain potassium dihydrogen phosphate slurry. The potassium dihydrogen phosphate wet product is obtained by centrifugation and the wet product is dried to obtain potassium dihydrogen phosphate.

2. The method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction as described in claim 1, characterized in that, In step (3), the extraction temperature is 25~60℃, the extraction time is 15~30min, and the stirring speed is 150~300r / min.

3. The method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction as described in claim 1, characterized in that, In step (1), the potassium oxide content in potassium chloride is 58%~62%; the phosphorus pentoxide content in calcium phosphate is 35%~41%.

4. The method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction as described in claim 1, characterized in that, The 98% sulfuric acid solution is pumped into the reaction system at a rate of 30-50 ml / min.

5. The method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction as described in claim 1, characterized in that, The volume ratio of components A, B, and C is 3~8:3~8:2~4.

6. The method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction as described in claim 1, characterized in that, In step (4), the cooling rate of the concentrated potassium dihydrogen phosphate filtrate is 0.2~0.8℃ / min.

7. The method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction as described in claim 1, characterized in that, In step (3), the organic phase of extraction is back-extracted with 25%~28% ammonia water, and the organic phase is the regenerated extractant; the oil-water ratio of the back-extracted phase is 4~9:1, the back-extraction temperature is 25~65℃, the back-extraction time is 15~30min, and the stirring speed is 150~300r / min.

8. The method for preparing industrial-grade potassium dihydrogen phosphate using metathesis extraction as described in claim 7, characterized in that, The hydrogen chloride generated in step (1) is adsorbed with ammonia water to obtain an ammonium chloride solution; then it is combined with the back-extracted water and concentrated, with the temperature controlled at 70~80℃. After concentration, cooling and crystallization, ammonium chloride is obtained by solid-liquid separation.

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