Method for preparing battery-grade lithium carbonate by carbonizing lithium carbonate

Abstract

The invention discloses a method for preparing battery-grade lithium carbonate by carbonizing lithium carbonate, which comprises the following steps: uniformly mixing industrial-grade lithium carbonate with pure water to prepare slurry, conveying the slurry to a reaction kettle, and controlling the temperature in the reaction kettle to be 5-10 DEG C and the pressure to be 4-5 MPa; generating liquid CO2 from the dry ice, conveying the liquid CO2 into a reaction kettle, and carrying out carbonization reaction to obtain a lithium bicarbonate solution; and carrying out solid-liquid separation on the lithium bicarbonate solution, and then carrying out purification and pyrolysis to obtain the battery-grade lithium carbonate. According to the method for preparing the battery-grade lithium carbonate through carbonization of the lithium carbonate, the liquid CO2 is adopted to replace gaseous CO2 to participate in the reaction, the mass transfer rate in the reaction process is increased, efficient carbonization reaction is promoted, meanwhile, high-purity battery-grade lithium carbonate can be obtained easily, and the recovery effect of the lithium carbonate in industrial lithium carbonate is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium carbonate purification, and in particular relates to a method for preparing battery-grade lithium carbonate by carbonizing lithium carbonate. Background Art

[0002] Lithium carbonate (Li2CO3) is a basic lithium compound with a variety of industrial uses. It can be converted into a variety of other lithium compounds and is widely used in lithium battery cathode materials, medicine, aerospace, metallurgy, welding, ceramics, lithium alloys, etc. With the development of new energy vehicles, the demand and price of battery-grade lithium carbonate will continue to rise.

[0003] At present, further purification of industrial-grade lithium carbonate can obtain battery-grade lithium carbonate, and the commonly used technologies include recrystallization, carbonization decomposition, carbonization precipitation, and causticization. Among the existing public lithium carbonate purification methods, the carbonization decomposition method is widely used in industrial production due to its short process flow, mother liquor recycling, high recovery rate, and simple operation. The specific reaction equation is as follows:

[0004] Carbonization reaction: Li2CO3(s)+CO2(g)+H2O(l)→2LiHCO3(aq);

[0005] Thermal decomposition reaction: 2LiHCO3(aq)→Li2CO3(↓)+CO2(g)+H2O(l).

[0006] When using the carbonization decomposition method to purify lithium carbonate, optimizing the carbonization reaction is a key step. Considering that the solubility of lithium carbonate and gaseous CO2 in water decreases with decreasing temperature, and the carbonization reaction is an exothermic reaction (adiabatic temperature rise is between 10-13°C), the mass transfer and heat transfer performance during the reaction process is obviously insufficient due to the inherent shortcomings of the above-mentioned reaction raw materials. Therefore, further improving the carbonization efficiency is of great significance for the production of high-purity lithium carbonate. Summary of the invention

[0007] Based on the above technical problems, the present invention provides a method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate. By using liquid CO2 instead of gaseous CO2 to participate in the reaction, the mass transfer rate in the reaction process is increased, which promotes the efficient carbonization reaction. At the same time, it is also helpful to obtain high-purity battery-grade lithium carbonate and improve the recovery effect of lithium carbonate in industrial lithium carbonate.

[0008] The present invention provides a method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate, comprising the following steps:

[0009] S1. Mix industrial-grade lithium carbonate and pure water to form a slurry, and then transport it to a reactor. Control the temperature in the reactor to 5-10°C and the pressure to 4-5MPa;

[0010] S2, generating liquid CO2 from dry ice and then transporting it to a reactor for carbonization reaction to obtain a lithium bicarbonate solution;

[0011] S3, after solid-liquid separation, the lithium bicarbonate solution is purified and pyrolyzed to obtain the battery-grade lithium carbonate.

[0012] In the present invention, liquid CO2 is used instead of gaseous CO2 to participate in the carbonization reaction, which not only increases the mass transfer rate in the reaction process, improves the reaction efficiency and the lithium bicarbonate concentration, but also can effectively remove impurities in industrial lithium carbonate, improve the purity of lithium carbonate, and help to finally obtain battery-grade lithium carbonate.

[0013] Preferably, in step S1, the mass ratio of the industrial-grade lithium carbonate to pure water is 1:5-20.

[0014] Preferably, in step S2, the feed flow rate of the slurry is 5-300 mL / min, and the feed flow rate of the liquid CO2 is 1-10 mL / min.

[0015] Preferably, in step S2, the liquid residence time is 5-15 min.

[0016] Preferably, in step S3, the solid-liquid separation is achieved by filtration through a filter membrane;

[0017] Preferably, the pore size of the filter membrane is 0.1-1 μm.

[0018] Preferably, in step S3, the purification is achieved by ion exchange resin.

[0019] Preferably, the ion exchange resin is a phosphate-type ion exchange resin;

[0020] Preferably, the phosphoric acid type ion exchange resin is obtained by grafting polystyrene resin white balls with acryloyl chloride and then copolymerizing with vinyl phosphoric acid and vinyl dimethyl phosphate.

[0021] In the present invention, various inorganic cations in the lithium bicarbonate solution are directionally removed by ion exchange resin, thereby ensuring the quality stability of the lithium bicarbonate solution and the final product quality; and phosphoric acid groups are introduced into the polystyrene resin white balls, thereby increasing the adsorption sites for heavy metal ions (Ca, Mg, etc.), and the phosphate ions can also be complexed with the heavy metal ions, thereby enhancing the adsorption capacity of the resin and facilitating the improvement of the adsorption effect thereof.

[0022] Preferably, in step S3, the pyrolysis temperature is 70-90° C. and the time is 0.5-2 h.

[0023] The present invention also provides a battery-grade lithium carbonate, which is prepared by the above method.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] The method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate of the present invention is that after industrial-grade lithium carbonate is mixed with pure water, a carbonization reaction is carried out with liquid CO2, which not only increases the mass transfer rate in the reaction process and promotes the carbonization reaction, but also converts lithium carbonate into lithium bicarbonate that is easily soluble in water to the greatest extent, removes insoluble impurities in industrial lithium carbonate by filtering, and then effectively removes ionic impurities in industrial-grade lithium carbonate by phosphoric acid ion exchange resin, further improves the purity of lithium carbonate, thereby meeting the requirements of battery-grade lithium carbonate. The purity of lithium carbonate is made higher than the purity requirement of battery-grade lithium carbonate, and by strictly controlling the process conditions and the material dosage ratio, the loss of lithium ions can be reduced, and the recovery effect of lithium carbonate in industrial lithium carbonate can be improved.

[0026] The present invention can not only reduce the loss of lithium ions and improve the recovery effect of lithium carbonate in industrial-grade lithium carbonate by cooperating with each other through the above steps, but also further improve the purity of the obtained battery-grade lithium carbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of the method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate. DETAILED DESCRIPTION

[0028] Hereinafter, the present invention will describe the technical solution in detail through specific embodiments, but it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

[0029] Example 1

[0030] Reference Figure 1 This embodiment provides a method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate, which specifically includes:

[0031] (1) adding industrial grade lithium carbonate (purity of 99.05% and average particle size of 20 μm) to deionized water at a mass ratio of 1:10, stirring and mixing to prepare lithium carbonate slurry; delivering the lithium carbonate slurry to the reactor from the bottom inlet of the reactor at a flow rate of 85 mL / min, adjusting the pressure in the reactor to 4.5 MPa, and reducing the temperature in the high-pressure reactor to 5° C. through a cooling jacket and then keeping it constant;

[0032] (2) introducing nitrogen into a storage tank containing dry ice, and reacting with the dry ice to generate liquid CO2 under the driving force of nitrogen pressure; injecting the liquid CO2 into a reactor through an insulated pipe at a flow rate of 6 mL / min, turning on a stirrer placed on the top of the reactor, stirring at a rate of 200 r / min to perform a carbonization reaction, and the liquid residence time in the reactor is 10 min, to obtain a high-pressure lithium bicarbonate solution; after the high-pressure lithium bicarbonate solution is depressurized to normal pressure, a lithium bicarbonate solution is obtained;

[0033] (3) filtering the lithium bicarbonate solution through a filter cloth with a pore size of 1 μm to remove insoluble impurities, and then passing the solution through an exchange column filled with a phosphoric acid type ion exchange resin at a rate of 10 BV / h to remove impurity ions, thereby obtaining a purified lithium bicarbonate solution; wherein the phosphoric acid type ion exchange resin is prepared by the following method:

[0034] Add polystyrene resin white balls (white spherical granular resin) into dichloromethane and swell for 4 hours, then add acryloyl chloride twice the mass of the polystyrene resin white balls, then add anhydrous aluminum chloride twice the mass of the polystyrene resin white balls, stir and react at a rate of 100 rpm at 40°C for 3 hours, filter, wash and dry to obtain polystyrene resin white balls grafted with acryloyl chloride; add polystyrene resin white balls grafted with acryloyl chloride into N,N-dimethylformamide and swell for 12 hours, then add vinyl phosphonic acid 5 times the mass of the polystyrene resin white balls grafted with acryloyl chloride and vinyl dimethyl phosphate 1 times the mass of the polystyrene resin white balls grafted with acryloyl chloride, then add benzoyl peroxide 1wt% of the mass of the polystyrene resin white balls grafted with acryloyl chloride, heat to 80°C under nitrogen protection, react for 6 hours, filter, wash and dry to obtain the phosphoric acid type ion exchange resin.

[0035] (4) The purified lithium bicarbonate solution is transferred to a pyrolysis kettle, heated to 70° C. and then pyrolyzed, stirred at high speed for 1 hour, and centrifuged to obtain a precipitated solid, which is dried at 150° C. for 2 hours to obtain the battery-grade lithium carbonate.

[0036] Example 2

[0037] This embodiment provides a method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate. The specific method is as described in Example 1, except that in step (1), after the lithium carbonate slurry is transported to the reactor from the bottom inlet of the reactor at a flow rate of 140 mL / min, the pressure in the reactor is adjusted to 5 MPa, and the temperature in the high-pressure reactor is reduced to 10°C and maintained constant through a cooling jacket; in step (2), liquid CO2 is injected into the reactor through an insulated pipe at a flow rate of 10 mL / min, the agitator placed on the top of the reactor is turned on, and the carbonization reaction is carried out at a rate of 200 r / min. The liquid residence time in the reactor is 15 min, and a high-pressure lithium bicarbonate solution is obtained.

[0038] Example 3

[0039] This embodiment proposes a method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate. The specific method is referred to Example 1, except that in step (1), after the lithium carbonate slurry is transported to the reactor from the bottom inlet of the reactor at a flow rate of 15 mL / min, the pressure in the reactor is adjusted to 4 MPa, and the temperature in the high-pressure reactor is reduced to 5°C and maintained constant through a cooling jacket; in step (2), liquid CO2 is injected into the reactor through an insulated pipe at a flow rate of 1 mL / min, the agitator placed on the top of the reactor is turned on, and the carbonization reaction is carried out at a rate of 200 r / min. The liquid residence time in the reactor is 5 min, and a high-pressure lithium bicarbonate solution is obtained.

[0040] Comparative Example 1

[0041] This comparative example proposes a method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate. The specific method is as described in Example 1, except that in step (2), gaseous CO2 is injected into the reactor at a flow rate of 2.8 L / min, the agitator placed on the top of the reactor is turned on, and the agitator is stirred at a rate of 200 r / min to carry out the carbonization reaction. The liquid residence time in the reactor is 120 min, and a high-pressure lithium bicarbonate solution is obtained.

[0042] Comparative Example 2

[0043] This comparative example proposes a method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate. The specific method is as described in Example 1, except that in step (3), the lithium bicarbonate solution is filtered through a filter cloth with a pore size of 1 μm to remove insoluble impurities, and then passed through an exchange column filled with D732 ion exchange resin at a rate of 10 BV / h to remove impurity ions.

[0044] The impurity indicators of the industrial-grade lithium carbonate used in the above examples and comparative examples and the obtained battery-grade lithium carbonate are shown in Table 1 below.

[0045] Table 1

[0046]

[0047]

[0048] It can be seen from the results in Table 1 above that the purity and various impurities of the battery-grade lithium carbonate prepared by the present invention are within the national standard range, meeting the requirements of battery-grade lithium carbonate; this shows that the method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate provided by the present invention can effectively purify industrial-grade lithium carbonate to meet the requirements of battery-grade lithium carbonate and reduce the loss rate of lithium carbonate in industrial-grade lithium carbonate.

[0049] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate, characterized in that: The steps include: S1. Mix industrial-grade lithium carbonate and pure water to form a slurry, and then transport it to a reactor. Control the temperature in the reactor to 5-10°C and the pressure to 4-5MPa; S2, generating liquid CO2 from dry ice and then transporting it to a reactor for carbonization reaction to obtain a lithium bicarbonate solution; S3, after solid-liquid separation, the lithium bicarbonate solution is purified and pyrolyzed to obtain the battery-grade lithium carbonate.

2. The method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate according to claim 1, characterized in that: In step S1, the mass ratio of the industrial-grade lithium carbonate to pure water is 1:5-20.

3. The method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate according to claim 1 or 2, characterized in that: In step S2, the feed flow rate of the slurry is 5-300 mL / min, and the feed flow rate of the liquid CO2 is 1-10 mL / min.

4. The method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate according to any one of claims 1 to 3, characterized in that: In step S2, the liquid residence time is 5-15 minutes.

5. The method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate according to any one of claims 1 to 4, characterized in that: In step S3, the solid-liquid separation is achieved by filtration through a filter membrane; Preferably, the pore size of the filter membrane is 0.1-1 μm.

6. The method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate according to any one of claims 1 to 5, characterized in that: In step S3, the purification is achieved by ion exchange resin.

7. The method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate according to claim 6, characterized in that: The ion exchange resin is a phosphoric acid type ion exchange resin; Preferably, the phosphoric acid type ion exchange resin is obtained by grafting polystyrene resin white balls with acryloyl chloride and then copolymerizing with vinyl phosphoric acid and vinyl dimethyl phosphate.

8. The method for preparing battery-grade lithium carbonate by carbonization of lithium carbonate according to any one of claims 1 to 7, characterized in that: In step S3, the pyrolysis temperature is 70-90°C and the time is 0.5-2h.

9. A battery-grade lithium carbonate, characterized in that: The invention is prepared by the method according to any one of claims 1 to 8.

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