A method for preparing high-purity high-density lithium tetraborate powder in a liquid phase using battery-grade lithium carbonate

Abstract

This invention discloses a method for preparing high-purity, high-density lithium tetraborate powder using battery-grade lithium carbonate in the liquid phase. The method involves a low-temperature reaction of lithium carbonate and boric acid at 26-28°C to form an intermediate solution of borate, facilitating solution purification. By controlling the lithium carbonate concentration at 20-50 g / L and combining it with a high-temperature reaction, a supersaturated water glass solution of lithium tetraborate is generated, which is then spray-dried to obtain high-density lithium tetraborate powder. Therefore, the product generated by this method contains only lithium tetraborate and no other byproducts. This method uses battery-grade lithium carbonate with relatively low purity and moderate price, and boric acid with a purity of 99.9% to obtain a powder with a purity of 99.99% and a density of 1.39 g / cm³. 3 The preparation process of lithium tetraborate is simple, easy to operate, and inexpensive, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium tetraborate preparation technology, specifically a method for preparing high-purity, high-density lithium tetraborate powder using battery-grade lithium carbonate in the liquid phase. Background Technology

[0002] Boron compounds are diverse and structurally complex due to the presence of two types of coordination bonds, especially borates. Unlike other inorganic salts, borates exhibit complex and variable structures and properties, and their water solubility is characterized by the coexistence of multiple particles and interactions between boron-oxygen anions, resulting in borates appearing in various forms in aqueous solutions. When preparing lithium tetraborate using lithium salts and boron-containing compounds in the liquid phase, various byproducts may be generated. Furthermore, existing methods for preparing high-purity lithium tetraborate often use high-purity lithium hydroxide as the lithium salt raw material. However, the strong alkalinity of lithium hydroxide solutions makes the preparation process of high-purity lithium hydroxide complex and difficult, and the high price of high-purity lithium hydroxide significantly increases the production cost of high-purity lithium tetraborate. On the other hand, if low-purity lithium salt raw materials are used, it is difficult to obtain 99.99% high-purity lithium tetraborate without proper purification processes. Therefore, the complexity of the reaction products and the preparation of high-purity lithium salt raw materials make the preparation of high-purity lithium tetraborate extremely difficult.

[0003] Furthermore, borates commonly exhibit supersaturated dissolution, meaning that borates do not precipitate as solute in solution but instead form a water glass solution. Even after evaporation and concentration, the solute does not precipitate, resulting in no wet borate powder. Current methods for precipitating borates from water glass solutions involve adding ethanol. However, this method has the following problems in practice: 1. Adding ethanol to the borate water glass solution causes borates to precipitate instantly, but these borates are gel-like and highly viscous, causing them to stick to the stirring device and leading to stirring failure. 2. The resulting gel-like borates require further addition of large amounts of ethanol under strong stirring to obtain borate powder, resulting in high solvent consumption. Therefore, existing methods for precipitating borates using ethanol have poor production continuity, require sophisticated equipment, and are costly.

[0004] Furthermore, with changing market demand, there is a shortage of high-purity, high-density lithium tetraborate, but the density of lithium tetraborate prepared by existing methods is only 0.7-0.8 g / cm³. 3 This method cannot meet market demand. Chinese invention patent CN102838125B uses a method of mechanically crushing lithium tetraborate, then melting it at high temperature, and finally quenching and crystallizing it with water to obtain high-density lithium tetraborate. However, this method has high energy consumption, complex processes, and high costs. In addition, the multiple processing steps result in a large loss of lithium tetraborate products. Summary of the Invention

[0005] Based on the above, the purpose of this invention is to provide a method for preparing high-purity, high-density lithium tetraborate powder using industrial-grade lithium carbonate in the liquid phase, so as to solve the technical problems of difficulty in preparing high-purity, high-density lithium tetraborate, high cost and large product loss of existing preparation methods.

[0006] A method for preparing high-purity, high-density lithium tetraborate powder using battery-grade lithium carbonate in a liquid phase includes the following steps:

[0007] (1) Take battery-grade lithium carbonate, add 99.9% boric acid, mix evenly to obtain mixed powder;

[0008] (2) Place the mixed powder from step (1) into a reaction vessel, add pure water, start stirring, and carry out a low-temperature reaction at 26-28℃ to obtain a clear and transparent solution; the amount of pure water added is based on the concentration of lithium carbonate in the solution being 40-50 g / L.

[0009] (3) The clear and transparent solution in step (2) is first filtered through a 3-stage precision filter, then impurities are removed by a 3-stage cation exchange resin, and finally filtered through a 1-stage precision filter to obtain the purified solution;

[0010] (4) The purified liquid in step (3) is subjected to a high-temperature reaction under the action of reflux and condensation, with a reaction temperature of 120-135℃, to obtain the reaction solution;

[0011] (5) The reaction solution in step (4) is spray-dried while hot. The inlet temperature of the spray dryer is 180-190℃ and the outlet temperature is 70-80℃ to obtain lithium tetraborate powder.

[0012] (6) Wash and dry the lithium tetraborate from step (5) to obtain high-purity, high-density lithium tetraborate powder.

[0013] As a further preferred embodiment of the technical solution of the present invention, in step (1), the amount of boric acid used is 1.06-1.08 times the theoretical amount of the reaction.

[0014] Furthermore, in step (2), the low-temperature reaction time is 50-80 min.

[0015] Furthermore, in step (3), the precision filtration refers to filtration using a filter membrane with a pore size of 0.02 μm.

[0016] Furthermore, in step (4), the high-temperature reaction time is 8-9 hours.

[0017] Furthermore, in step (5), the spray drying time is 6-10 seconds.

[0018] Further, in step (6), the washing process is as follows: wash with electronic water at a solid-liquid ratio of 1-1:3 for 20-40 minutes.

[0019] Further, in step (6), the drying process is as follows: the lithium tetraborate washed with ethanol is placed in a vacuum oven and dried at 400-450℃ for 2-3 hours.

[0020] Furthermore, the vacuum degree of the vacuum oven is -0.08 MPa.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention involves reacting lithium carbonate with boric acid at a low temperature of 26-28°C to form an intermediate solution of borate, which facilitates the purification of the solution and subsequent production of high-purity lithium tetraborate. By controlling the lithium carbonate concentration at 20-50 g / L and coordinating with a high-temperature reaction, a supersaturated water glass solution of lithium tetraborate is generated, which facilitates spray drying and yields high-density lithium tetraborate powder.

[0023] 2. To address the problem of multiple particles coexisting in borate solutions, resulting in complex and variable structures that easily form various compositions and prevent the production of a single lithium tetraborate, this invention incorporates a high-temperature reaction stage. This stage aims to convert complex borates into a single-component lithium tetraborate. Two key factors ensure the success of this high-temperature reaction: First, the reaction temperature must be between 120-135°C; second, boric acid must be in excess. If only the theoretical amounts of lithium carbonate and boric acid are added, the precipitation of lithium tetraborate later reduces the lithium and boron content in the solution, leading to a higher likelihood of lithium metaborate as the final product. Therefore, under the high-temperature conditions set in this invention, combined with controlled lithium carbonate concentration, only lithium tetraborate is produced without any other byproducts.

[0024] 3. This invention prepares high-density lithium tetraborate using a spray drying method. The drying speed is fast, the process is simple and easy to operate, and energy consumption is low. It also solves the problem of severe lithium tetraborate loss caused by the multiple processes involved in patent CN102838125B, which involves mechanical crushing, high-temperature melting, and finally water quenching and crystallization. The recovery rate of lithium tetraborate is high. Furthermore, the obtained lithium tetraborate powder has good dispersibility and flowability, and a high product density, reaching up to 1.39 g / cm³. 3 The density obtained using existing methods is 0.7-0.8 g / cm³. 3 It is nearly twice as effective as that of other drugs.

[0025] 4. The method of this invention uses battery-grade lithium carbonate with low purity, moderate price, and easy preparation, and boric acid with a purity of 99.9% to obtain a product with a purity of 99.99% and a density of 1.39 g / cm³. 3 The preparation process of lithium tetraborate is simple, easy to operate, and inexpensive, making it suitable for large-scale industrial production. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments.

[0027] Currently, the industry requires a B2O3:Li2O ratio between 0.2125 and 0.2145 for high-purity lithium tetraborate.

[0028] In the following embodiments of the present invention, the battery-grade lithium carbonate has a purity of 99.5%, and the boric acid has a purity of 99.9%. Precision filtration refers to filtration using a filter membrane with a pore size of 0.02 μm. The cation exchange resin is a 001×7 cation exchange resin.

[0029] Example 1

[0030] (1) Take 50g of battery-grade lithium carbonate, add 175.69g of boric acid, mix evenly to obtain a mixed powder;

[0031] (2) Place the mixed powder from step (1) into a 3L reactor, add 1L of pure water, turn on the stirring, and react at 26℃ for 60min to obtain a clear and transparent solution with a lithium carbonate concentration of 50g / L.

[0032] (3) The clear and transparent solution in step (2) is first filtered through a 3-stage precision filter, then impurities are removed by a 3-stage cation exchange resin, and finally filtered through a 1-stage precision filter to obtain the purified solution;

[0033] (4) The purified liquid in step (3) is subjected to a high-temperature reaction under the action of reflux condensation. The reaction temperature is 110℃ and the reaction time is 8h to obtain a lithium tetraborate solution that is similar to a glass aqueous solution.

[0034] (5) The reaction liquid in step (4) is spray-dried while hot. The inlet air drying temperature is 180℃, the outlet air drying temperature is 75℃, and the spray drying time is 6s to obtain lithium tetraborate powder.

[0035] (6) The lithium tetraborate from step (5) was washed with electronic grade ethanol at a solid-liquid ratio of 1:2 for 30 min, and then placed in an oven and dried at 400°C for 2 h to obtain high-purity, high-density lithium tetraborate powder.

[0036] The lithium tetraborate powder prepared in this embodiment has a purity of 99.992% and a density of 1.39 g / cm³. 3 .

[0037] Example 2

[0038] (1) Take 500g of battery-grade lithium carbonate, add 1756.9g of boric acid, mix evenly to obtain mixed powder;

[0039] (2) Place the mixed powder from step (1) into a 3L reactor, add 1L of pure water, turn on the stirring, and react at 26℃ for 60min to obtain a clear and transparent solution with a lithium carbonate concentration of 50g / L.

[0040] (3) The clear and transparent solution in step (2) is first filtered through a 3-stage precision filter, then impurities are removed by a 3-stage cation exchange resin, and finally filtered through a 1-stage precision filter to obtain the purified solution;

[0041] The solution is purified by passing it through a cation exchange resin for impurity removal, and then through a first-stage precision filtration to obtain the purified solution.

[0042] (4) The purified liquid in step (3) is subjected to a high-temperature reaction under the action of reflux condensation. The reaction temperature is 110℃ and the reaction time is 8h to obtain a lithium tetraborate solution that is similar to a glass aqueous solution.

[0043] (5) The reaction liquid in step (4) is spray-dried while hot. The inlet air drying temperature is 400℃, the outlet air drying temperature is 80℃, and the spray drying time is 6s to obtain lithium tetraborate powder.

[0044] (6) The lithium tetraborate from step (5) was washed with electronic grade ethanol at a solid-liquid ratio of 1:1 for 30 min, and then placed in an oven and dried at 400°C for 2 h to obtain high-purity, high-density lithium tetraborate powder.

[0045] The lithium tetraborate powder prepared in this embodiment has a purity of 99.991% and a density of 1.391 g / cm³. 3 .

[0046] Examples 3-9

[0047] Examples 3-9 are identical to Example 1 in all other steps, except that the concentration of lithium carbonate is adjusted to 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, and 50 g / L. The detection data of lithium tetraborate prepared using different concentrations of lithium carbonate are shown in Table 1.

[0048] Table 1. Detection data of lithium tetraborate prepared from lithium carbonate of different concentrations.

[0049]

[0050] As shown in Table 1, when the concentration of lithium carbonate is 40-50 g / L, the purity of the prepared lithium tetraborate is ≥99.99%. Furthermore, the density of the prepared lithium tetraborate is 1.39 g / cm³. 3 This meets market demand for high-density lithium tetraborate. Furthermore, the B2O3:Li2O mass ratio in the tested product is between 0.2125 and 0.2145, which meets the requirements.

[0051] Examples 10-18

[0052] Examples 10-18 are identical to Example 1 in all other steps, except that the high-temperature reaction temperature in step (4) is adjusted to 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, and 150℃. The detection data of the prepared lithium tetraborate are shown in Table 2.

[0053] Table 2. Detection data of lithium tetraborate prepared at different high-temperature reaction temperatures.

[0054]

[0055] As can be seen from the data in Table 2, when the reaction temperature of step (4) is 120-135℃, the purity of the prepared lithium tetraborate is ≥99.99%. The mass ratio of B2O3:Li2O is also within the required range of 0.2125-0.2145. Considering energy consumption and cost, 120℃ can be selected as the reaction temperature.

[0056] Examples 19-24

[0057] Examples 19-24 are identical to Example 1 in all other steps, except for the amount of boric acid used in step (1). The effect of the amount of boric acid on the purity of lithium tetraborate is shown in Table 3.

[0058] Table 3. Effect of boric acid dosage on the purity of lithium tetraborate

[0059]

[0060] As shown in Table 3, when the amount of boric acid used is 1.06-1.08 times the theoretical amount, the purity of the prepared lithium tetraborate is ≥99.99%, and the tested B2O3:Li2O mass ratio is also within the required range of 0.2125-0.2145. Therefore, it is preferable to use 1.06-1.08 times the theoretical amount of lithium borate.

[0061] Examples 25-30

[0062] Examples 25-30 are identical to Example 1 in all other steps, except for the change in the low-temperature reaction temperature in step (2). The effect of the low-temperature reaction temperature on the purity of lithium tetraborate is shown in Table 4.

[0063] Table 4. Effect of low-temperature reaction temperature on the purity of lithium tetraborate

[0064]

[0065] As shown in Table 4, when the low-temperature reaction temperature in step (2) is 26-28℃, the purity of the prepared lithium tetraborate is ≥99.99%, and the mass ratio of B2O3:Li2O is also within the required range of 0.2125-0.2145. Therefore, the optimal low-temperature reaction temperature is 26-28℃.

[0066] Examples 31-38

[0067] Examples 31-38 are identical to Example 1 in all other steps, except for the low-temperature reaction time in step (2). The effect of the low-temperature reaction time on the formation of a clear and transparent solution is shown in Table 5.

[0068] Table 5. Effect of low-temperature reaction time on the formation of a clear and transparent solution.

[0069]

[0070] As shown in Table 5, a clear and transparent solution can be formed after 50 minutes of low-temperature reaction in step (2). Therefore, a low-temperature reaction time of 50-80 minutes is preferred.

[0071] Examples 39-45

[0072] Examples 39-45 are identical to Example 1 in all other steps, except for the high-temperature reaction time in step (4). The effect of the high-temperature reaction time on the purity of lithium tetraborate is shown in Table 6.

[0073] Table 6. Effect of high-temperature reaction time on the purity of lithium tetraborate.

[0074]

[0075] As shown in Table 6, when the high-temperature reaction time in step (4) is 8-9 hours, the purity of the prepared lithium tetraborate is ≥99.99%, and the mass ratio of B2O3:Li2O is within the required range of 0.2125-0.2145. Therefore, the optimal high-temperature reaction time is 8-9 hours.

[0076] Examples 46-54

[0077] Examples 46-54 are identical to Example 1 in all other steps, except for the temperature of the spray drying inlet in step (5). The effect of the spray drying inlet temperature on the lithium tetraborate powder is shown in Table 7.

[0078] Table 7. Effect of spray drying inlet temperature on lithium tetraborate powder

[0079]

[0080] As can be seen from the data in Table 7, dry lithium tetraborate powder can be obtained when the air inlet temperature of spray drying in step (5) is 180-190℃. Therefore, the air inlet temperature of powder drying is preferably 180-190℃.

[0081] Examples 55-63

[0082] Examples 55-63 are identical to Example 1 in all other steps, except for the spray drying time in step (5). The effect of spray drying time on lithium tetraborate powder is shown in Table 8.

[0083] Table 8. Effect of spray drying time on lithium tetraborate powder

[0084]

[0085] As can be seen from the data in Table 8, dry lithium tetraborate powder can be obtained when the spray drying time in step (5) is greater than 6s. Therefore, the optimal spray drying time is 6-10s.

[0086] Examples 64-66

[0087] Examples 64-66 are identical to Example 1 in all other steps, except for the washing ratio in step (6). The effect of the washing ratio on the purity of lithium tetraborate is shown in Table 9.

[0088] Table 9. Effect of washing ratio on the purity of lithium tetraborate

[0089]

[0090] As shown in Table 9, when the solid-liquid ratio in step (6) is 1:1, 1:2, or 1:3, the purity of the obtained lithium tetraborate is ≥99.99%, and the mass ratio of B2O3:Li2O is also within the required range of 0.2125-0.2145. Therefore, a solid-liquid ratio of 1:1 is the preferred choice for the washing process.

[0091] Examples 64-66

[0092] Examples 64-66 are identical to Example 1 in all other steps, except for the drying temperature in step (6). The effect of drying temperature on the purity of lithium tetraborate is shown in Table 10.

[0093] Table 10 Effect of drying temperature on the purity of lithium tetraborate

[0094]

[0095] As shown in Table 10, when the drying temperatures in step (6) are 400℃, 410℃, 420℃, 430℃, 440℃, and 450℃, the purity of the prepared lithium tetraborate is ≥99.99%, and the mass ratio of B2O3:Li2O is within the required range of 0.2125-0.2145. Therefore, 400℃ is the preferred drying temperature.

[0096] Comparative Examples 1-5

[0097] Comparative Examples 1-5 followed the same steps as Example 1, except that step (3) of the purification process in Example 1 was removed. The purity of the obtained lithium tetraborate is shown in Table 11.

[0098] Table 11 Purity of lithium tetraborate prepared in Comparative Examples 1-5

[0099]

[0100] As can be seen from the five repeated examples of Comparative Examples 1-5, when lithium tetraborate is prepared using battery-grade lithium carbonate, without a purification process, the purity of the obtained lithium tetraborate is only 98%, and high-purity lithium tetraborate cannot be obtained.

[0101] Comparative Examples 6-11

[0102] Table 12 compares the energy consumption (Example 1) and lithium tetraborate powder recovery rate of the preparation of high-density lithium tetraborate by Chinese invention patent CN102838125B and the preparation of high-density lithium tetraborate by spray drying of the present invention.

[0103] Table 12 Comparison of energy consumption and lithium tetraborate powder recovery rate between the present invention and patent CN102838125B

[0104]

[0105] As can be seen from the six repeated examples in Comparative Examples 6-11, the energy consumption of Chinese Invention Patent CN102838125B in preparing high-density lithium tetraborate is approximately twice that of this invention. High energy consumption leads to high cost. Furthermore, the multiple processing steps also result in the loss of lithium tetraborate powder, leading to a reduced recovery rate.

Claims

1. A method for preparing high-purity, high-density lithium tetraborate powder using battery-grade lithium carbonate in the liquid phase, characterized in that, Includes the following steps: (1) Take battery-grade lithium carbonate, add 99.9% boric acid, mix evenly to obtain a mixed powder; the amount of boric acid used is 1.06-1.08 times the theoretical amount of the reaction. (2) Place the mixed powder from step (1) into a reaction vessel, add pure water, start stirring, and carry out a low-temperature reaction at 26-28℃ for 50-80 minutes to obtain a clear and transparent solution; the amount of pure water added is based on the concentration of lithium carbonate in the solution being 40-50 g / L. (3) The clear and transparent solution in step (2) is first filtered through a 3-stage precision filter, then impurities are removed by a 3-stage cation exchange resin, and finally filtered through a 1-stage precision filter to obtain the purified solution; (4) The purified liquid in step (3) is subjected to a high-temperature reaction under the action of condensation and reflux. The reaction temperature is 120-135℃ and the reaction time is 8-9h to obtain the reaction solution. (5) The reaction solution in step (4) is spray-dried while hot. The inlet temperature of the spray dryer is 180-190℃ and the outlet temperature is 70-80℃ to obtain lithium tetraborate powder. (6) Wash and dry the lithium tetraborate from step (5) to obtain high-purity, high-density lithium tetraborate powder.

2. The method for preparing high-purity, high-density lithium tetraborate powder using battery-grade lithium carbonate in the liquid phase as described in claim 1, characterized in that, In step (3), the precision filtration refers to filtration using a filter membrane with a pore size of 0.02 μm.

3. The method for preparing high-purity, high-density lithium tetraborate powder using battery-grade lithium carbonate in the liquid phase as described in claim 1, characterized in that, In step (5), the spray drying time is 6-10 seconds.

4. A method for preparing high-purity, high-density lithium tetraborate powder in the liquid phase using battery-grade lithium carbonate as described in any one of claims 1-3, characterized in that, In step (6), the washing process is as follows: wash with electronic grade ethanol at a solid-liquid ratio of 1:1-3 for 20-40 minutes.

5. A method for preparing high-purity, high-density lithium tetraborate powder in the liquid phase using battery-grade lithium carbonate as described in any one of claims 1-3, characterized in that, In step (6), the drying process is as follows: the washed lithium tetraborate is placed in a vacuum oven and dried at 400-450℃ for 2-3 hours.

6. The method for preparing high-purity, high-density lithium tetraborate powder using battery-grade lithium carbonate in the liquid phase as described in claim 5, characterized in that, The vacuum oven has a vacuum level of -0.08 MPa.

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