CN-121974316-A - Preparation method of ferric phosphate dihydrate with controlled crystal form duty ratio

CN121974316ACN 121974316 ACN121974316 ACN 121974316ACN-121974316-A

Abstract

The invention relates to the field of ferric phosphate dihydrate preparation, in particular to a preparation method of ferric phosphate dihydrate with a controlled crystal form ratio, which comprises the steps of preparing monoclinic crystal suspension induction liquid; the oxidation reaction comprises the steps of adding monoclinic crystal suspension induction liquid into a synthesis kettle, heating, adding hydrogen peroxide and ferrous dihydrogen phosphate solution simultaneously under strong stirring, regulating the feeding flow of the hydrogen peroxide and the ferrous dihydrogen phosphate solution simultaneously, controlling the reaction residence time, obtaining slurry A after the residence time is reached, aging the slurry A, and adding hydrogen peroxide to finally obtain the ferric phosphate dihydrate product. According to the invention, through the control of the flow rate of hydrogen peroxide and ferrous liquid and the cooperative control of the temperature and the residence time, the regulation and control of the monoclinic phase crystal form and the orthorhombic crystal form proportion of the obtained ferric phosphate dihydrate can be realized, and the duty ratio of the monocrystal form in the ferric phosphate dihydrate is controlled.

Inventors

HUA TIAN
MA HANG
ZHOU YANJIE
ZHANG JINYUAN
ZHA ZUOTONG
LI XING
ZHANG JIE
CHEN ZHANGHONG
ZHENG JIE

Assignees

云南云天化股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260226

Claims (10)

1. The preparation method of the ferric phosphate dihydrate with the controlled crystal form ratio is characterized by comprising the following steps of: step (1) preparing monoclinic crystal suspension induced liquid Mixing monoclinic phase ferric phosphate dihydrate with mother liquor to prepare monoclinic crystal suspension induced liquid, wherein the mother liquor is a clear liquid phase system obtained after solid ferric phosphate dihydrate products are removed through solid-liquid separation after ferric phosphate crystallization reaction is finished; Step (2) oxidation reaction Adding monoclinic crystal suspension induced liquid into a synthesis kettle, heating to 60-80 ℃, simultaneously adding hydrogen peroxide and ferrous dihydrogen phosphate solution under strong stirring, simultaneously adjusting the feeding flow of the hydrogen peroxide and ferrous dihydrogen phosphate solution, and obtaining slurry A after the reaction residence time is reached; Step (3) aging Heating the slurry A, stirring, aging and precipitating, continuously growing crystals in the aging process, continuously adding hydrogen peroxide solution into the reaction solution after the precipitation is finished, continuously stirring to obtain crystal product slurry B, filtering, washing with deionized water, and drying to obtain the ferric phosphate dihydrate product.
2. The method for producing iron phosphate dihydrate according to claim 1, characterized in that in step (1), iron phosphate dihydrate of monoclinic phase crystal form accounts for 97% or more of the total mass.
3. The method for producing iron phosphate dihydrate according to claim 1, characterized in that in the step (1), monoclinic phase iron phosphate dihydrate and a mother solution are mixed according to a mass ratio of 1:4-20, the mother solution is a solution with a phosphorus mass concentration of 3-4.5% and an iron ion concentration of 0.10-0.11%, or after the crystallization reaction of iron phosphate dihydrate is finished, solid iron phosphate dihydrate product is removed by solid-liquid separation, and the clarified liquid is obtained.
4. The method for producing iron phosphate dihydrate according to claim 1, characterized in that in step (1), the iron ion concentration in the monoclinic phase iron phosphate dihydrate is 360-365 g/L, the solid content in the monoclinic crystal suspension induction liquid is 6-15%, and the pH value is 0.8-1.2.
5. The method for producing iron phosphate dihydrate of claim 1, characterized in that in step (2), the addition amount of the monoclinic crystal suspension induction liquid is 10-30% of the effective volume of the synthesis reactor.
6. The method for preparing iron phosphate dihydrate according to claim 1, characterized in that in the step (2), hydrogen peroxide and ferrous dihydrogen phosphate solution are added according to a flow ratio of 0.0322-0.0326, and the reaction residence time is 30-120 min; When the orthorhombic crystal form is required to be obtained, crystal growth is carried out at the reaction temperature of 75-80 ℃, and when the monoclinic crystal form is required to be obtained, crystal growth is carried out at the reaction temperature of 60-70 ℃; and when the monoclinic crystal form duty ratio needs to be increased, reacting for 30-60 min, and when the orthorhombic crystal form duty ratio needs to be increased, reacting for 90-120 min.
7. The method for preparing ferric phosphate dihydrate of claim 1, characterized in that in step (2), the molar ratio of iron content in the added ferrous dihydrogen phosphate solution to hydrogen peroxide is 1:0.8-1:1.3, the mass fraction of hydrogen peroxide used is 26-30%, and the iron ion concentration of the ferrous dihydrogen phosphate solution is 30-65 g/L.
8. The method for preparing ferric phosphate dihydrate of claim 1, wherein when preparing ferric phosphate dihydrate product with monoclinic phase ratio more than 90%, hydrogen peroxide and ferrous phosphate solution are added according to flow ratio of 0.0324-0.0325 in step (2).
9. The method for preparing ferric phosphate dihydrate of claim 1, wherein when preparing ferric phosphate dihydrate product with monoclinic phase ratio more than 97%, in step (2), monoclinic crystal suspension induced liquid is heated to 65-70 ℃, hydrogen peroxide and ferrous phosphate solution are added according to flow ratio of 0.0325.
10. The method for preparing iron phosphate dihydrate according to claim 1, characterized in that in the step (3), the aging temperature is 65-85 ℃, the aging precipitation is carried out for 1-3 hours, the mass fraction of the hydrogen peroxide used is 26-30%, the flow rate of the hydrogen peroxide added is 0.4-0.75 mol/min, and the dripping time is 20-30 min.

Description

Preparation method of ferric phosphate dihydrate with controlled crystal form duty ratio Technical Field The invention relates to the field of ferric phosphate dihydrate preparation, in particular to a preparation method of ferric phosphate dihydrate with a controlled crystal form ratio. Background The existing method for preparing ferric phosphate dihydrate is mostly a liquid phase synthesis method, and iron salt and phosphate radical are used as raw materials to react to obtain products mainly in monoclinic crystal form and orthorhombic crystal form. However, the crystal form of the product is difficult to control. The existing method for controlling the crystal form of ferric phosphate dihydrate is to change the pH value of a solution by adding an acid-base regulator so as to influence the growth of the crystal form, or realize the conversion of the crystal form by high-temperature calcination after synthesis. But the prior art has obvious defects that on one hand, the control precision of the pH value adjustment on the crystal form proportion is low, the crystal forms in the product are easy to mix due to the fluctuation of the local pH value, and on the other hand, the post calcination treatment can increase the production process and the energy consumption, and the dehydration of ferric phosphate dihydrate can be caused in the high-temperature process, so that the purity of the product is influenced. These problems lead to the difficulty of stable production of ferric phosphate dihydrate with the required crystal form ratio by the existing method, and obvious performance differences exist in application fields such as battery materials and the like of ferric phosphate dihydrate with different crystal form ratios. In the prior art, although the regulation and control of the crystal forms are carried out, pH regulation is not needed, and calcination is not needed for obtaining the ferric phosphate dihydrate, but the method can only roughly control the ratio of orthorhombic to monoclinic. Disclosure of Invention The invention aims to provide a preparation method of ferric phosphate dihydrate with a controlled crystal form ratio, which can better realize the regulation and control of the ratio of monoclinic phase crystals and orthorhombic system crystals in ferric phosphate dihydrate products. The technical scheme of the invention is as follows: A preparation method of ferric phosphate dihydrate with controlled crystal form duty ratio comprises the following steps: step (1) preparing monoclinic crystal suspension induced liquid Mixing monoclinic phase ferric phosphate dihydrate with mother liquor to prepare monoclinic crystal suspension induced liquid, wherein the mother liquor is a clear liquid phase system obtained after solid ferric phosphate dihydrate products are removed through solid-liquid separation after ferric phosphate crystallization reaction is finished; Step (2) oxidation reaction Adding monoclinic crystal suspension induced liquid into a synthesis kettle, heating to 60-80 ℃, simultaneously adding hydrogen peroxide and ferrous dihydrogen phosphate solution under strong stirring, simultaneously adjusting the feeding flow of the hydrogen peroxide and ferrous dihydrogen phosphate solution, and obtaining slurry A after the reaction residence time is reached; Step (3) aging Heating the slurry A, stirring, aging and precipitating, continuously growing crystals in the aging process, continuously adding hydrogen peroxide solution into the reaction solution after the precipitation is finished, continuously stirring to obtain crystal product slurry B, filtering, washing with deionized water, and drying to obtain the ferric phosphate dihydrate product. The method can realize the regulation and control of the monoclinic phase crystal form and the orthorhombic crystal form proportion of the obtained ferric phosphate dihydrate by controlling the flow rate of the hydrogen peroxide and the ferrous liquid and the cooperative control of the temperature and the residence time, and can control the proportion of the monoclinic phase in the ferric phosphate dihydrate to be more than 97 percent by regulating and controlling the proportion of the monoclinic phase in the ferric phosphate dihydrate product. The method has the advantages of simple process and low energy consumption, saves the post calcination procedure, reduces the energy consumption and shortens the production period. The crystal form duty ratio of the product can be controlled by only adjusting the physical factors of the reaction system, a pH regulator is not used, impurity ions introduced by pH regulation are avoided, and the product purity is improved. The method can stably produce the iron phosphate, can reduce the large particle size of the iron phosphate product by improving the proportion of the orthorhombic system, can improve the electrical property of the lithium iron phosphate, and can provide the iron phosphate products with different co