High-purity iron phosphate material and preparation method thereof

Abstract

The application relates to the technical field of iron phosphate preparation, in particular to a high-purity iron phosphate material and a preparation method thereof. The preparation method of the high-purity iron phosphate material provided by the application comprises the following steps: mixing polystyrene microspheres, chloromethyl methyl ether, a first catalyst and an organic solvent to obtain primary modified polystyrene microspheres; mixing the primary modified polystyrene microspheres, aminomethyl phosphonic acid, a second catalyst, a cocatalyst and an organic solvent to obtain secondary modified polystyrene microspheres; mixing an iron source solution and a phosphorus source solution, then adding the secondary modified polystyrene microspheres to carry out reaction, and baking to obtain the high-purity iron phosphate material. The iron phosphate material obtained by the method has low impurity content and high tap density, and the preparation method is relatively simple, low in energy consumption and convenient to operate.

Description

Technical Field

[0001] This invention relates to the field of iron phosphate preparation technology, specifically to a high-purity iron phosphate material and its preparation method. Background Technology

[0002] Lithium iron phosphate (LFP) is an important battery material in new energy batteries, and its application is becoming increasingly widespread. Currently, LFP batteries are the mainstream energy storage batteries, and the demand for LFP materials is also growing. Iron phosphate is widely used in ceramics, pigments, food, and other fields, and it is also an important precursor for the synthesis of LFP materials. Therefore, research on the production and preparation of high-purity iron phosphate materials is urgently needed.

[0003] Existing methods for preparing ferric phosphate generally use phosphorus and iron sources as reactants, then obtain ferric phosphate dihydrate through a heating co-precipitation reaction, and finally obtain ferric phosphate material through calcination. However, due to limitations in the purity of the reactants and the addition of other auxiliary components during the reaction process, it is unavoidable to introduce impurity ions, especially impurity cations, into the reaction system. These impurities affect the purity of the ferric phosphate material and consequently its subsequent applications. Summary of the Invention

[0004] In order to overcome the defect of high impurity content in ferric phosphate materials obtained by existing ferric phosphate preparation methods, a high-purity ferric phosphate material and its preparation method are provided.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a high-purity iron phosphate material includes the following steps:

[0007] 1) Polystyrene microspheres, chloromethyl ether, the first catalyst and organic solvent were mixed and reacted. After the reaction was completed, the mixture was filtered, the filter cake was washed and dried to obtain primary modified polystyrene microspheres.

[0008] 2) After mixing the primary modified polystyrene microspheres, aminomethylphosphonic acid, the second catalyst, the co-catalyst and the organic solvent, the reaction was carried out. After the reaction was completed, hydrochloric acid solution was added to the reaction system and stirred. After stirring was completed, the mixture was filtered, the filter cake was washed and dried to obtain the secondary modified polystyrene microspheres.

[0009] 3) Mix the iron source solution and the phosphorus source solution, then add the secondary modified polystyrene microspheres, heat the reaction solution to 80-100℃, stir the reaction at 80-100℃, filter after the stirring reaction is completed, mix the filter cake and water again, let stand, remove the suspended secondary modified polystyrene microspheres, heat the mixture to 85-100℃ to continue the reaction, filter after the reaction is completed, wash the filter cake, dry it, and then calcine the dried product to obtain the high-purity iron phosphate material.

[0010] Preferably, in step 1), the mass ratio of polystyrene microspheres, chloromethyl ether, the first catalyst and the organic solvent is (1-2):(2-5):(0.1-0.4):(20-50).

[0011] Preferably, the reaction temperature in step 1) is 50-60℃ and the reaction time is 10-20h;

[0012] The polystyrene microspheres mentioned in step 1) have a particle size of 2-6 μm, the organic solvent is selected from at least one of tetrahydrofuran and dichloromethane, and the first catalyst is selected from zinc chloride;

[0013] In step 1), the washing step uses ethanol for washing.

[0014] Preferably, in step 2), the mass ratio of the primary modified polystyrene microspheres, aminomethylphosphonic acid, the second catalyst, the co-catalyst, and the organic solvent is (1-2):(0.3-0.8):(0.8-2.0):(0.1-0.5):(20-50);

[0015] The reaction temperature in step 2) is 50-60℃, and the reaction time is 8-15h.

[0016] Preferably, in step 2), the second catalyst is selected from at least one of sodium methoxide and sodium ethoxide, the co-catalyst is selected from sodium iodide, and the organic solvent is selected from at least one of methanol and ethanol;

[0017] In step 2), the amount of hydrochloric acid solution added is 3-8 times the mass of the one-time modified polystyrene microspheres, and the mass fraction of the hydrochloric acid solution is 10-20%.

[0018] In step 2), the stirring time is 0.2-1 h, the stirring temperature is room temperature, and the filter cake is washed with methanol and water.

[0019] Preferably, the iron source solution in step 3) is selected from ferric sulfate solution, and the concentration of ferric sulfate solution is 0.1-0.3 mol / L; the phosphorus source solution is selected from ammonium dihydrogen phosphate solution, and the concentration of ammonium dihydrogen phosphate solution is 0.2-0.5 mol / L.

[0020] In step 3), the molar ratio of iron to phosphorus in the solution after mixing the iron source solution and the phosphorus source solution is 1:(1.01-

[0021] 1.5).

[0022] Preferably, in step 3), the amount of secondary modified polystyrene microspheres added is 5%-10% of the mass of ferric sulfate in the ferric sulfate solution.

[0023] Preferably, in step 3), the reaction is stirred at 80-100°C for 10-40 minutes at a stirring speed of 110-200 rpm.

[0024] After the stirring reaction is completed in step 3), the temperature of the reaction solution should be kept at 80-100℃ during filtration.

[0025] Preferably, in step 3), the amount of water added in the re-mixing step is 1-2 times the volume of the iron source solution;

[0026] The settling time mentioned in step 3) is 0.2-1.5 hours;

[0027] In step 3), the reaction time continues for 1-3 hours, and water is used for washing the filter cake.

[0028] Preferably, the roasting temperature in step 3) is 620-670℃ and the roasting time is 1-5h.

[0029] The beneficial effects of this invention are:

[0030] The method for preparing iron phosphate material provided by the present invention firstly modifies polystyrene microspheres by chloromethylation to obtain primary modified polystyrene microspheres, and then modifies the primary modified polystyrene microspheres by phosphonic acid to obtain secondary modified polystyrene microspheres. Furthermore, this invention involves mixing an iron source and a phosphorus source, then adding the aforementioned secondary modified polystyrene microspheres. The iron and phosphorus sources react at 80-100°C to obtain products such as ferric phosphate monohydrogen phosphate and ferric phosphate dihydrogen phosphate. Ferric phosphate monohydrogen phosphate and ferric phosphate dihydrogen phosphate have low solubility in water at 80-100°C and exist in solid form in the reaction system. At this point, hot filtration is performed, and most impurities are retained in the solution. Since secondary modified polystyrene microspheres are added to the system of this invention, the surface of the secondary modified polystyrene microspheres has abundant phosphate groups. In the initial stage of the reaction, they react with the iron source in the reaction solution to obtain products such as ferric phosphate monohydrogen phosphate and / or ferric phosphate dihydrogen phosphate. These products are distributed on the surface of the polystyrene microspheres, forming numerous micronuclei. The presence of these micronuclei makes it easy for the reaction products of the iron and phosphorus sources to approach the surface of the polystyrene microspheres and separate from the impurity ions in the reaction system, facilitating subsequent filtration and removal. Afterward, the filter cake obtained by filtration is mixed with water again to remove the secondary modified polystyrene microspheres, and the reaction continues. The reaction product is calcined to obtain high-purity iron phosphate material. The iron phosphate material obtained by the method of the present invention has a low impurity content. During the preparation process, the reaction product particles will continuously collide with the microspheres due to the presence of the secondary modified polystyrene microspheres, which improves the tap density of the product. At the same time, the preparation method of the present invention is relatively simple, has low energy consumption, and is easy to operate. Detailed Implementation

[0031] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0032] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0033] Example 1

[0034] This embodiment provides a method for preparing high-purity iron phosphate material, including the following steps:

[0035] 1) Mix 1.5g of polystyrene microspheres with a particle size of 5μm, 3g of chloromethyl methyl ether, 0.3g of zinc chloride and 30g of tetrahydrofuran, and react at 55℃ for 15h. After the reaction is completed, filter, wash the filter cake with ethanol and dry it to obtain primary modified polystyrene microspheres.

[0036] 2) Mix 1.2g of primary modified polystyrene microspheres, 0.6g of aminomethylphosphonic acid, 1g of sodium methoxide, 0.2g of sodium iodide and 30g of methanol, and react at 55℃ for 10h. After the reaction is complete, add 5g of 15% hydrochloric acid solution to the reaction system, stir at room temperature for 0.5h, filter after stirring, wash the filter cake with methanol and water respectively, and dry to obtain secondary modified polystyrene microspheres;

[0037] 3) Mix 100 ml of 0.1 mol / L ferric sulfate solution and 100 ml of 0.22 mol / L ammonium dihydrogen phosphate solution, then add 0.2 g of secondary modified polystyrene microspheres. Heat the reaction solution to 85°C and stir at 85°C for 30 min at a stirring speed of 150 rpm. After the reaction is complete, filter immediately while hot (maintain the reaction solution temperature at 85°C during filtration). Mix the filter cake with 150 ml of water again and let it stand for 0.5 h. After removing the suspended secondary modified polystyrene microspheres, heat the mixture to 92°C and continue the reaction for 1.5 h. After the reaction is complete, filter, wash the filter cake with water, dry it, and then calcine the dried product at 650°C for 4 h to obtain the high-purity ferric phosphate material.

[0038] Example 2

[0039] This embodiment provides a method for preparing high-purity iron phosphate material, including the following steps:

[0040] 1) Mix 1.5g of polystyrene microspheres with a particle size of 5μm, 3.5g of chloromethyl methyl ether, 0.2g of zinc chloride and 30g of tetrahydrofuran, and react at 60℃ for 20h. After the reaction is completed, filter, wash the filter cake with ethanol and dry to obtain primary modified polystyrene microspheres.

[0041] 2) Mix 1.2g of primary modified polystyrene microspheres, 0.8g of aminomethylphosphonic acid, 1.5g of sodium methoxide, 0.2g of sodium iodide and 30g of methanol, and react at 55℃ for 12h. After the reaction is complete, add 5g of 15% hydrochloric acid solution to the reaction system and stir at room temperature for 0.5h. After stirring, filter, wash the filter cake with methanol and water respectively, and dry to obtain secondary modified polystyrene microspheres.

[0042] 3) Mix 100 ml of 0.1 mol / L ferric sulfate solution and 100 ml of 0.25 mol / L ammonium dihydrogen phosphate solution, then add 0.3 g of secondary modified polystyrene microspheres. Heat the reaction solution to 88°C and stir at 88°C for 30 min at a stirring speed of 150 rpm. After the reaction is complete, filter while hot (maintain the reaction solution temperature at 88°C during filtration). Mix the filter cake with 150 ml of water again and let it stand for 0.5 h. After removing the suspended secondary modified polystyrene microspheres, heat the mixture to 96°C and continue the reaction for 1.5 h. After the reaction is complete, filter, wash the filter cake with water, dry it, and then calcine the dried product at 650°C for 4.5 h to obtain the high-purity ferric phosphate material.

[0043] Example 3

[0044] This embodiment provides a method for preparing high-purity iron phosphate material, including the following steps:

[0045] 1) Mix 1.5g of polystyrene microspheres with a particle size of 5μm, 3.2g of chloromethyl methyl ether, 0.5g of zinc chloride and 30g of tetrahydrofuran, and react at 60℃ for 14h. After the reaction is completed, filter, wash the filter cake with ethanol and dry to obtain primary modified polystyrene microspheres.

[0046] 2) Mix 1.2g of primary modified polystyrene microspheres, 0.7g of aminomethylphosphonic acid, 1.8g of sodium methoxide, 0.2g of sodium iodide and 30g of methanol, and react at 55℃ for 10h. After the reaction is complete, add 5g of 15% hydrochloric acid solution to the reaction system, stir at room temperature for 0.5h, filter after stirring, wash the filter cake with methanol and water respectively, and dry to obtain secondary modified polystyrene microspheres;

[0047] 3) Mix 100 ml of 0.1 mol / L ferric sulfate solution and 100 ml of 0.24 mol / L ammonium dihydrogen phosphate solution, then add 0.4 g of secondary modified polystyrene microspheres. Heat the reaction solution to 88°C and stir at 88°C for 30 min at a stirring speed of 150 rpm. After the reaction is complete, filter while hot (keeping the reaction solution temperature at 88°C during filtration). Mix the filter cake with 150 ml of water again and let it stand for 0.5 h. After removing the suspended secondary modified polystyrene microspheres, heat the mixture to 92°C and continue the reaction for 2 h. After the reaction is complete, filter, wash the filter cake with water, dry it, and then calcine the dried product at 650°C for 5 h to obtain the high-purity ferric phosphate material.

[0048] Comparative Example 1

[0049] This comparative example provides a method for preparing high-purity iron phosphate material, including the following steps:

[0050] Mix 100 ml of 0.1 mol / L ferric sulfate solution and 100 ml of 0.22 mol / L ammonium dihydrogen phosphate solution. Heat the reaction solution to 85°C and stir at 85°C for 30 min at a stirring speed of 150 rpm. After the reaction is complete, filter while hot (maintain the reaction solution temperature at 85°C during filtration). Mix the filter cake with 150 ml of water again and let it stand for 0.5 h. Heat the mixture to 92°C and continue the reaction for 1.5 h. After the reaction is complete, filter, wash the filter cake with water, dry it, and then calcine the dried product at 650°C for 4 h to obtain the high-purity ferric phosphate material.

[0051] Comparative Example 2

[0052] This comparative example provides a method for preparing high-purity iron phosphate material, including the following steps:

[0053] 1) Mix 1.5g of polystyrene microspheres with a particle size of 5μm, 3g of chloromethyl methyl ether, 0.3g of zinc chloride and 30g of tetrahydrofuran, and react at 55℃ for 15h. After the reaction is completed, filter, wash the filter cake with ethanol and dry it to obtain primary modified polystyrene microspheres.

[0054] 2) Mix 100 ml of 0.1 mol / L ferric sulfate solution and 100 ml of 0.22 mol / L ammonium dihydrogen phosphate solution, then add 0.2 g of primary modified polystyrene microspheres. Heat the reaction solution to 85°C and stir at 85°C for 30 min at a stirring speed of 150 rpm. After the reaction is complete, filter while hot (maintain the reaction solution temperature at 85°C during filtration). Mix the filter cake with 150 ml of water again and let stand for 0.5 h. After removing the suspended primary modified polystyrene microspheres, heat the mixture to 92°C and continue the reaction for 1.5 h. After the reaction is complete, filter, wash the filter cake with water, dry it, and then calcine the dried product at 650°C for 4 h to obtain the high-purity ferric phosphate material.

[0055] Test case

[0056] The iron phosphate materials prepared in the above embodiments and comparative examples were tested, and some test results are shown in Table 1.

[0057] Table 1

[0058]

[0059] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-purity iron phosphate material, characterized in that, Includes the following steps: 1) Polystyrene microspheres, chloromethyl ether, a first catalyst and an organic solvent were mixed and reacted. After the reaction was completed, the mixture was filtered, the filter cake was washed and dried to obtain primary modified polystyrene microspheres. 2) After mixing the primary modified polystyrene microspheres, aminomethylphosphonic acid, the second catalyst, the co-catalyst and the organic solvent, the reaction was carried out. After the reaction was completed, hydrochloric acid solution was added to the reaction system and stirred. After stirring was completed, the mixture was filtered, the filter cake was washed and dried to obtain the secondary modified polystyrene microspheres. 3) Mix the iron source solution and the phosphorus source solution, then add the secondary modified polystyrene microspheres, heat the reaction solution to 80-100℃, stir the reaction at 80-100℃, filter after the stirring reaction is completed, mix the filter cake and water again, let stand, remove the suspended secondary modified polystyrene microspheres, heat the mixture to 85-100℃ to continue the reaction, filter after the reaction is completed, wash the filter cake, dry it, and then calcine the dried product to obtain the high-purity iron phosphate material.

2. The preparation method according to claim 1, characterized in that, In step 1), the mass ratio of polystyrene microspheres, chloromethyl methyl ether, the first catalyst and the organic solvent is (1-2):(2-5):(0.1-0.4):(20-50).

3. The preparation method according to claim 1 or 2, characterized in that, In step 1), the reaction temperature is 50-60℃ and the reaction time is 10-20h; The polystyrene microspheres mentioned in step 1) have a particle size of 2-6 μm, the organic solvent is selected from at least one of tetrahydrofuran and dichloromethane, and the first catalyst is selected from zinc chloride; In step 1), the washing step uses ethanol for washing.

4. The preparation method according to claim 1, characterized in that, In step 2), the mass ratio of the primary modified polystyrene microspheres, aminomethylphosphonic acid, the second catalyst, the co-catalyst, and the organic solvent is (1-2):(0.3-0.8):(0.8-2.0):(0.1-0.5):(20-50). The reaction temperature described in step 2) is 50-60℃, and the reaction time is 8-15h.

5. The preparation method according to claim 1, characterized in that, In step 2), the second catalyst is selected from at least one of sodium methoxide and sodium ethoxide, the co-catalyst is selected from sodium iodide, and the organic solvent is selected from at least one of methanol and ethanol; In step 2), the amount of hydrochloric acid solution added is 3-8 times the mass of the one-time modified polystyrene microspheres, and the mass fraction of the hydrochloric acid solution is 10-20%. In step 2), the stirring time is 0.2-1 h, the stirring temperature is room temperature, and the filter cake is washed with methanol and water.

6. The preparation method according to claim 1, characterized in that, In step 3), the iron source solution is selected from ferric sulfate solution, and the concentration of ferric sulfate solution is 0.1-0.3 mol / L; the phosphorus source solution is selected from ammonium dihydrogen phosphate solution, and the concentration of ammonium dihydrogen phosphate solution is 0.2-0.5 mol / L. In step 3), the molar ratio of iron to phosphorus in the solution after mixing the iron source solution and the phosphorus source solution is 1:(1.01-1.5).

7. The preparation method according to claim 6, characterized in that, In step 3), the amount of secondary modified polystyrene microspheres added is 5%-10% of the mass of ferric sulfate in the ferric sulfate solution.

8. The preparation method according to claim 1, characterized in that, In step 3), the reaction is stirred at 80-100℃ for 10-40 minutes at a stirring speed of 110-200 rpm. After the stirring reaction is completed in step 3), the temperature of the reaction solution should be kept at 80-100℃ during filtration.

9. The preparation method according to claim 1, characterized in that, In step 3), the amount of water added in the re-mixing step is 1-2 times the volume of the iron source solution; The settling time mentioned in step 3) is 0.2-1.5 hours; In step 3), the reaction time continues for 1-3 hours, and water is used for washing the filter cake. In step 3), the roasting temperature is 620-670℃ and the roasting time is 1-5h.

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