A kind of synthetic preparation method of iron phosphate

Abstract

The present invention belongs to the technical field of chemical products, and in particular to a method for synthesizing and preparing ferric phosphate. The steps include: preparing sodium hydroxide solution; adding β-cyclodextrin to deionized water, heating to 90 ° C, preparing a saturated solution of β-cyclodextrin; adding a saturated solution of β-cyclodextrin to a reactor, adding a sodium hydroxide solution thereto, heating to 60 ° C for insulation, stirring continuously for 4 hours, and then cooling to room temperature to obtain a β-cyclodextrin / NaOH inclusion compound solution A; weighing an iron source and dissolving it in deionized water, then adding a phosphorus source, stirring continuously, and controlling the temperature to 50-70 ° C, preparing a mixed solution B; adding H2O2 to the mixed solution B, until the solution is reddish brown; continuing to add the prepared β-cyclodextrin / NaOH inclusion compound solution A to adjust the pH value of the mixed solution to 1.5-2.5, stirring continuously for 0.5-2 hours, heating to 80-100 ° C for insulation for 1-3 hours, generating FePO4·2H2O particles with good crystallinity, washing and drying to obtain FePO4·2H2O. The invention has short process flow, safe and reliable production process and stable product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical products, and particularly relates to a synthetic preparation method of ferric phosphate. Background Art

[0002] With the rapid development of the lithium-ion battery industry, lithium iron phosphate batteries have become the ideal cathode material for the new generation of lithium-ion batteries due to their advantages such as wide sources of raw materials, low prices, good safety performance and long cycle life. As an important precursor for the preparation of lithium iron phosphate, the preparation of iron phosphate is of great significance to the production of lithium iron phosphate, and the quality of iron phosphate products has an important impact on the performance of lithium iron phosphate.

[0003] At present, the mainstream process for synthesizing iron phosphate is to use ferrous sulfate and phosphate as raw materials. The production process of iron phosphate is an intermittent coprecipitation method, in which ferrous sulfate is made into a solution, hydrogen peroxide is added for oxidation, and then a certain proportion of phosphate is added. After adjusting the pH with alkaline solution, the solution is synthesized and converted, washed, impurities are removed, and calcined to obtain the iron phosphate product. A typical Chinese patent with the publication number "CN 107317029 B" discloses a method for preparing iron phosphate: the iron source is mixed with an acid solution and filtered, the filtrate is mixed with phosphoric acid, the pH value is adjusted to 0.5-1, and then the pH value is adjusted to 1.5-2.5 after mixing with an inducer, and a precipitation reaction is carried out to obtain iron phosphate.

[0004] There is still room for improvement in the process of preparing iron phosphate by existing processes. Typically, the existing process uses alkali solution (usually ammonia water or sodium hydroxide) to adjust the pH and has the following problems: when ammonia water is used to adjust the pH, ammonium salts and air purification treatment devices need to be added later, the overall production cost is high, and the applicability is not strong. When sodium hydroxide is used to adjust the pH, the following problems are also faced: if a high concentration of sodium hydroxide solution is added, the instantaneous local concentration will be too large, which is not conducive to the consistency of the product; if a low concentration of sodium hydroxide solution is used, not only will the amount of wastewater treatment increase, but the yield will also decrease, and the production cost will be greatly increased.

[0005] Cyclodextrin (CD) is a green, biodegradable and cost-effective cyclic oligosaccharide compound, which can be divided into α-CD, β-CD and γ-CD according to the number of glucose units. Among them, β-CD is the most widely used one. It has a hydrophilic edge and a moderately hydrophobic molecular cavity, which can provide hydrophobic binding sites for inorganic ions. β-cyclodextrin is compounded with sodium hydroxide to prepare a β-cyclodextrin / NaOH inclusion complex solution; in the process of preparing iron phosphate, the β-cyclodextrin / NaOH inclusion complex solution is used to stably adjust the pH value, so that a stable iron phosphate product can be prepared. The production process is highly stable and the production cost can be greatly reduced.

[0006] In view of the above situation, the present invention is proposed. Summary of the invention

[0007] The present invention aims to solve the above technical problems and provides a method for synthesizing and preparing ferric phosphate. The method has a simple process flow, a safe and reliable production process, high stability, and the obtained product has small performance fluctuations and stable quality.

[0008] The technical solution of the present invention is as follows: a method for synthesizing and preparing ferric phosphate, the method comprising the following steps:

[0009] (1) adding sodium hydroxide particles into deionized water to prepare a sodium hydroxide solution;

[0010] (2) adding β-cyclodextrin into deionized water and heating the water to 90° C. to prepare a saturated β-cyclodextrin solution;

[0011] (3) adding the saturated β-cyclodextrin solution prepared in step (2) into a reaction kettle, and simultaneously adding the sodium hydroxide solution prepared in step (1) thereto, heating to 60° C., stirring continuously for 4 h, and then cooling to room temperature to obtain a β-cyclodextrin / NaOH inclusion complex solution A;

[0012] (4) Weighing a certain amount of iron source and dissolving it in deionized water, then adding a certain amount of phosphorus source, stirring continuously, and controlling the temperature at 50-70° C. to prepare a mixed solution B;

[0013] (5) Add H to the mixed solution B obtained in step (4) 2 O 2 , until the solution turns reddish brown; continue to add the β-cyclodextrin / NaOH inclusion complex solution A obtained in step (3) to the mixed solution B to adjust the pH value of the mixed solution to 1.5-2.5, continue stirring for 0.5-2h, raise the temperature to 80-100℃ and keep warm for 1-3h to generate FePO with good crystallinity 4 ·2H 2 O particles, washed and dried to obtain FePO 4 ·2H 2 O.

[0014] Preferably, in step (1), the concentration of the sodium hydroxide solution is 1.0-3.5 mol / L.

[0015] Preferably, in step (4), the iron source is any one of ferrous sulfate, ferric nitrate or ferric sulfate.

[0016] Preferably, in step (4), the phosphorus source is any one of phosphoric acid, sodium phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate or potassium phosphate.

[0017] Preferably, in step (4), the molar ratio of the elements Fe and P in the mixed solution B is 1.0:1.0-1.5.

[0018] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0019] The product obtained by the present invention has small performance fluctuation and stable quality. Specifically, the present invention makes a breakthrough improvement on the existing iron phosphate preparation process. When using alkali solution to adjust the pH value of the solution to precipitate iron phosphate, a homemade β-cyclodextrin / NaOH inclusion solution is selected. The β-cyclodextrin / NaOH inclusion solution can slowly and stably release hydroxide ions, which can effectively ensure the pH consistency in the precursor solution and effectively avoid the problem of instantaneous local excessive concentration in the solution and poor product uniformity; at the same time, the β-cyclodextrin / NaOH inclusion solution is used to slowly and stably release hydroxide ions, which is also beneficial to the precipitation of the iron phosphate product, and can effectively improve the yield of the product.

[0020] The process flow of the present invention is short, the production process is safe and reliable, and the stability is high. Specifically, it can be seen from the preparation method of the present invention that it is not only the preparation of the β-cyclodextrin / NaOH inclusion compound solution, but also the process of preparing the ferric phosphate product. The entire production process is controlled at normal pressure and below 100° C. The entire production process is safe and reliable, and the stability is high. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1

[0023] A method for synthesizing ferric phosphate, the method comprising the following steps:

[0024] First, a β-cyclodextrin / NaOH inclusion complex solution A is prepared for use. The specific method is as follows: sodium hydroxide particles are added to deionized water to prepare a sodium hydroxide solution with a concentration of 1 mol / L; β-cyclodextrin is added to deionized water and heated to 90° C. to prepare a saturated β-cyclodextrin solution; the prepared saturated β-cyclodextrin solution is added to a reaction kettle, and the same volume of the sodium hydroxide solution prepared above is added thereto, heated to 60° C. and kept warm, stirred continuously for 4 hours, and then cooled to room temperature to obtain a β-cyclodextrin / NaOH inclusion complex solution A for use;

[0025] Then, the iron phosphate precursor was prepared as follows: the iron source FeSO 4 7H 2 O, phosphorus source H 3 PO 4Dissolve in deionized water to prepare 1 mol / L FeSO 4 solution and 1 mol / L H 3 PO 4 solution; take 0.5L of prepared FeSO 4 Solution and H 3 PO 4 solution, then H 3 PO 4 The solution was slowly added with FeSO 4 The solution was stirred continuously and the temperature was controlled at 50-70°C to prepare a mixed solution B. H 2 O 2 , until the solution turns reddish brown; continue to add the prepared β-cyclodextrin / NaOH inclusion complex solution A to the mixed solution B to adjust the pH value of the mixed solution to 1.5-2.5, continue stirring for 0.5-2h, heat to 80-100℃ and keep warm for 1-3h to generate FePO with good crystallinity 4 ·2H 2 O particles, washed, dried and weighed. FePO 4 ·2H 2 O mass is 93.135g, FePO 4 ·2H 2 The yield of O was 99.61%.

[0026] Example 2

[0027] First, NaOH solution A is prepared for use. The specific method is as follows: sodium hydroxide particles are added to deionized water to prepare a sodium hydroxide solution with a concentration of 1 mol / L for use.

[0028] The iron phosphate precursor was prepared as follows: the iron source FeSO 4 7H 2 O, phosphorus source H 3 PO 4 Dissolve in deionized water to prepare 1 mol / L FeSO 4 solution and 1 mol / L H 3 PO 4 solution; take 0.5L of prepared FeSO 4 Solution and H 3 PO 4 solution, then H 3 PO 4 The solution was slowly added with FeSO 4 The solution was stirred continuously and the temperature was controlled at 50-70°C to prepare a mixed solution B. H 2 O 2, until the solution turns reddish brown; continue to add the prepared NaOH solution A to the mixed solution B to adjust the pH value of the mixed solution to 1.5-2.5, continue stirring for 0.5-2h, heat to 80-100℃ and keep warm for 1-3h to generate FePO 4 ·2H 2 O particles, washed, dried and weighed. FePO 4 ·2H 2 O mass is 71.276g, FePO 4 ·2H 2 The yield of O was 76.23%.

[0029] Comparative Example 1

[0030] The difference between this comparative example and Example 2 is that the concentration of NaOH solution A is different. The concentration of NaOH solution A prepared in this example is 0.5 mol / L. 4 ·2H 2 O mass is 79.591g, FePO 4 ·2H 2 The yield of O was 85.12%.

[0031] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for synthesizing iron phosphate, characterized in that: The method comprises the following steps: (1) adding sodium hydroxide particles into deionized water to prepare a sodium hydroxide solution; (2) adding β-cyclodextrin into deionized water and heating the water to 90° C. to prepare a saturated β-cyclodextrin solution; (3) adding the saturated β-cyclodextrin solution prepared in step (2) into a reaction kettle, and simultaneously adding the sodium hydroxide solution prepared in step (1) thereto, heating to 60° C., stirring continuously for 4 h, and then cooling to room temperature to obtain a β-cyclodextrin / NaOH inclusion complex solution A; (4) Weighing a certain amount of iron source and dissolving it in deionized water, then adding a certain amount of phosphorus source, stirring continuously, and controlling the temperature at 50-70° C. to prepare a mixed solution B; (5) Add H2O2 to the mixed solution B obtained in step (4) until the solution turns reddish brown; continue to add the β-cyclodextrin / NaOH inclusion complex solution A obtained in step (3) to the mixed solution B to adjust the pH value of the mixed solution to 1.5-2.5, continue stirring for 0.5-2h, raise the temperature to 80-100°C and keep it for 1-3h to generate FePO4·2H2O particles with good crystallinity, and wash and dry to obtain FePO4·2H2O.

2. The method for synthesizing ferric phosphate according to claim 1, characterized in that: In step (1), the concentration of the sodium hydroxide solution is 1.0-3.5 mol / L.

3. The method for synthesizing and preparing ferric phosphate according to claim 1, characterized in that: In step (4), the iron source is any one of ferrous sulfate, ferric nitrate or ferric sulfate.

4. The method for synthesizing and preparing ferric phosphate according to claim 1, characterized in that: In step (4), the phosphorus source is any one of phosphoric acid, sodium phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate or potassium phosphate.

5. The method for synthesizing and preparing ferric phosphate according to claim 1, characterized in that: In step (4), the molar ratio of the elements Fe and P in the mixed solution B is 1.0:1.0-1.5.