Preparation method of high-purity low-moisture lithium perchlorate

Abstract

The invention relates to the technical field of battery materials, and particularly discloses a preparation method of high-purity low-moisture lithium perchlorate, which comprises the following steps: A, adding lithium hydroxide monohydrate into a mixed solvent of an ester solvent and a benzene solvent; b, carrying out dehydration reaction, namely slowly dropwise adding perchloric acid into the mixed solution in the step A, heating to 120-150 DEG C after dropwise adding is completed, carrying out heat preservation for 6-8 hours, and stopping the reaction when the instantaneous solvent moisture separated from a reaction system does not exceed 1000ppm; c, filtering to remove impurities: filtering the reaction liquid to remove insoluble impurities; d, concentrating and crystallizing: concentrating the filtrate under reduced pressure to remove excessive solvent, stopping heating after crystals are separated out, cooling to room temperature, slowly dropwise adding poor solvent into the concentrated filtrate, then cooling and crystallizing, and filtering the filtrate to obtain a wet material; and E, drying in vacuum to obtain the lithium perchlorate crystal with the purity of 99.8% or above and the moisture value of less than 200ppm.

Description

Technical Field

[0001] The invention relates to the technical field of battery materials, and in particular to a method for preparing high-purity and low-moisture lithium perchlorate. Background Art

[0002] Lithium perchlorate (LiClO 4 ) has good solubility in a variety of organic solvents and exhibits relatively high ionic conductivity, especially the room temperature ionic conductivity of carbonates in electrolyte solvents can reach 9mS / cm. In addition, the electrochemical stability window of the electrolyte lithium salt electrolyte can reach 5.1Vvs.Li + / Li, has relatively good oxidation stability, this property also makes it possible to match some high-voltage positive electrode materials, thereby exerting the high energy density of lithium batteries.

[0003] At present, the preparation methods of lithium perchlorate are mainly divided into neutralization method and double decomposition method. The neutralization method is mostly based on water phase, and it is difficult to dehydrate in the later drying stage, and the water residue is high. For example, CN110835096A discloses a method for preparing high-purity anhydrous lithium perchlorate using battery-grade lithium hydroxide monohydrate, which uses lithium hydroxide monohydrate as a raw material, and is prepared by dissolving, neutralizing, filtering and removing impurities, concentrating and dehydrating, ethanol dehydration, cooling and crystallizing, vacuum drying and crushing once or twice. Although the water content of lithium perchlorate prepared by this method is less than 250ppm, and the main content is above 99.9%, it needs to be vacuum dried and crushed twice in the solid drying stage, with many operating steps, large equipment energy consumption, and low yield. For example, patent CN110085915A discloses a lithium perchlorate electrolyte solution and its preparation method, which is mainly based on double decomposition method, adding lithium salt and perchlorate to an organic solvent and removing moisture by passing inert gas, but the reaction degree of this method is limited, and the sodium element is not easy to remove. Summary of the invention

[0004] In order to solve the deficiencies in the above-mentioned prior art, the present invention aims to provide a method for preparing high-purity and low-moisture lithium perchlorate. The present invention uses lithium hydroxide monohydrate and perchloric acid as reaction raw materials, and removes moisture by separating water in the organic phase. Since the solubility of impurities in the solvent is limited, the lithium perchlorate prepared by this method has high yield, high purity, less than 200ppm of moisture, and is a powdered solid after crystallization without the need for crushing, while solving the problem of dehydration difficulties and sample drying and then crushing and screening in conventional methods. The preparation process of this method is simple, the equipment requirements are low, the solvent can be recycled, and it can be used for large-scale production. Due to its high purity and extremely low moisture content, the prepared lithium perchlorate can be directly used for the configuration of the electrolyte.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] A method for preparing high-purity and low-water perchlorate comprises the following steps:

[0007] A. Lithium hydroxide monohydrate is added to a reactor containing a mixed solvent of an ester solvent and a benzene solvent, wherein the reactor is equipped with a condenser and a water separator for subsequent dehydration. The ester solvent is a mixture of one or more of ethyl acetate, isopropyl acetate, methyl propionate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, and ethylene carbonate. The benzene solvent is a mixture of one or more of toluene, o-xylene, m-xylene, chlorobenzene, and p-xylene.

[0008] In the mixed solvent, the mass ratio of the ester solvent to the benzene solvent is 4:1-4, preferably 3:1-2, and more preferably 3:1.

[0009] The mass ratio of lithium hydroxide monohydrate to the mixed solvent is 1:6-11, and the preferred mass ratio is 1:7.5-9.

[0010] B. Dehydration reaction: at room temperature, under magnetic stirring, 70wt%-73wt% perchloric acid is slowly added dropwise to the mixed solution of step A, the molar ratio of lithium hydroxide monohydrate in the system to the added perchloric acid is 1-1.05:1, and perchloric acid and lithium hydroxide monohydrate undergo a neutralization reaction, and the dripping is completed for 1.5-2h. After the dripping is completed, the mixture is heated to 120-150°C and kept warm for 6-8h. The reaction is stopped when the instantaneous solvent water separated from the reaction system does not exceed 1000ppm. In this step, the reaction equation for the neutralization reaction between perchloric acid and lithium hydroxide monohydrate is: LiOH·H 2 O+HClO 4 →LiClO 4 +2H 2 O.

[0011] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0012] D. Concentration and crystallization: The filtrate filtered in the above step C is concentrated under reduced pressure at a vacuum pressure of -0.08 to -0.1 MPa and a temperature of 50-130°C to remove excess solvent. After crystals are precipitated, the heating is stopped, and after the temperature is cooled to room temperature, a poor solvent for perchlorate is slowly added dropwise to the concentrated filtrate, followed by cooling and crystallization at a cooling temperature of -5-5°C. The filtrate is filtered to obtain a wet material. The poor solvent is a mixture of one or more of dichloromethane, dichloroethane, 1-chloropropane, toluene, chlorobenzene, n-heptane, and cyclohexane. The amount of the poor solvent added is 3-6 times the mass of the theoretical target product.

[0013] E. The wet material filtered in step D is vacuum dried to obtain lithium perchlorate crystals with a purity of more than 99.8% and a moisture content of less than 200 ppm. The vacuum drying conditions are: drying temperature of 100-130° C., drying time of 6-12 hours, and vacuum pressure of 200-1000 mmHg.

[0014] Furthermore, in step A, the lithium hydroxide monohydrate can be replaced by sodium hydroxide, and finally in step E, sodium perchlorate crystals are obtained, the purity of the sodium perchlorate is above 99.8%, and the moisture value is less than 200 ppm.

[0015] In the method of the present invention, it is preferred to obtain high-purity and low-water lithium perchlorate, add lithium hydroxide monohydrate to a mixed organic solvent of esters and benzenes, slowly drop perchloric acid at room temperature for neutralization reaction to obtain lithium perchlorate containing a large amount of water, and then remove a large amount of water in the mixed organic phase by heating. Specifically, the raw materials lithium hydroxide monohydrate and perchloric acid are soluble in water and ester solvents, but insoluble in benzene solvents, and the lithium perchlorate produced by the reaction is soluble in water and ester solvents, but insoluble in benzene solvents. However, ester solvents and benzene solvents are miscible, so a mixed solution is formed, and no obvious stratification phenomenon occurs. In the method of the present invention, the reason for selecting a mixed solvent of ester solvents and benzene solvents instead of a single ester as the solvent is that the benzene solvent can increase the boiling point of the overall mixed solvent, which is more conducive to the evaporation of water and greatly shortens the time. Lithium perchlorate dissolves in water to form lithium perchlorate hydrate, but this problem can be avoided when it is dissolved in ester solvents. Of course, the mixing of benzene solvents will reduce the solubility of lithium perchlorate in ester solvents, and the water and part of the ester solvents will be evaporated due to water separation. Continuous action can remove all water and avoid the formation of lithium perchlorate trihydrate and agglomeration, which needs to be crushed again.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] (1) The present invention uses lithium hydroxide monohydrate / sodium hydroxide and perchloric acid as reaction raw materials, and removes water by separating water in the organic phase to avoid the formation of lithium perchlorate trihydrate and agglomeration; at the same time, the solubility of impurities in the solvent is limited. The lithium perchlorate / sodium perchlorate prepared by this method has high yield (more than 85%), high purity (more than 99.8%), less than 200 ppm of water, and is a powdery solid after crystallization without the need for crushing, thereby solving the problem of dehydration difficulty and crushing and screening of samples after drying in conventional methods.

[0018] (2) The preparation process of this method is simple, the equipment requirements are low, the solvent can be recycled, and it can be used for large-scale production.

[0019] (3) Due to its high purity and low water content, the prepared lithium perchlorate can be directly dissolved in the electrolyte. DETAILED DESCRIPTION

[0020] The applicant further describes the technical solution of the present invention in conjunction with specific embodiments below, but the scope of protection requested by the claims of the present invention is not limited to these embodiments.

[0021] Example 1

[0022] A method for preparing high-purity and low-water content lithium perchlorate comprises the following steps:

[0023] A. Take 100g of lithium hydroxide monohydrate and add it into a three-necked flask (equipped with a condenser and a water separator) containing a mixed solvent of 600g of ethyl methyl carbonate and 200g of chlorobenzene. Start stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0024] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. When the temperature is about 50°C, the reaction liquid becomes clear. The temperature is continuously raised to 120°C, and the solvent is stably separated. The reaction is continued at 120°C, and the separated solvent will be stratified (there is more water in the early stage, so the stratification is obvious). After 7 hours, the separated solvent has no obvious stratification phenomenon. At this time, the separated solvent is mainly ester with only a very small amount of water. The moisture value of the separated instantaneous sample (directly taken from the upper end of the water separator, about 1 mL) is monitored. When the reaction is kept warm for 7 hours, the moisture value of the instantaneous sample solvent is 2356 ppm; when the reaction is kept warm for 8 hours, the moisture value of the instantaneous sample solvent is 985 ppm, and the reaction is stopped.

[0025] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0026] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the temperature drops to room temperature, 700g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is dropped to 5°C for cooling and crystallization. After the filtrate is filtered, 276g of powdery lithium perchlorate wet material is obtained.

[0027] E. The wet material obtained by filtration in step D was vacuum dried at a vacuum pressure of 500 mmHg and a drying temperature of 110° C. for 8 h to obtain 208 g of white powdery crystals with a yield of 85.5%. The moisture content was 178.0 ppm and the IC purity was 99.9%.

[0028] Example 2

[0029] A method for preparing high-purity and low-water content lithium perchlorate comprises the following steps:

[0030] A. Take 100g of lithium hydroxide monohydrate and add it into a three-necked flask (equipped with a condenser and a water separator) containing a mixed solvent of 600g of dimethyl carbonate and 200g of chlorobenzene. Start stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0031] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. The reaction liquid becomes clear at about 60°C. The temperature is continuously raised to 130°C, and the solvent is stably separated. When the temperature is kept at 130°C for 6.5 hours, the separated solvent has no obvious stratification phenomenon. The instantaneous sample solvent water content is measured to be 1085ppm. After the reaction is kept at this temperature for 7 hours, the instantaneous sample solvent water content is measured to be 826ppm, and the reaction is stopped.

[0032] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0033] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the filtrate is cooled to room temperature, 750g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is cooled to 0°C for crystallization. After the filtrate is filtered, 284g of powdery lithium perchlorate wet material is obtained.

[0034] E. The wet material obtained by filtering in step D was vacuum dried at a vacuum pressure of 500 mmHg and a drying temperature of 120° C. for 8 h to obtain 211 g of white powdery crystals with a yield of 86.6%. The moisture content was 162.3 ppm and the IC purity was 99.9%.

[0035] Example 3

[0036] A method for preparing high-purity and low-water content lithium perchlorate comprises the following steps:

[0037] A. Take 100g of lithium hydroxide monohydrate and add it into a three-necked flask (equipped with a condenser and a water separator) containing a mixed solvent of 600g of diethyl carbonate and 200g of chlorobenzene. Start stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0038] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. The reaction liquid becomes clear at about 60°C. The temperature is continuously raised to 140°C, and the solvent is stably separated. When the temperature is kept at 140°C for 5 hours, the separated solvent has no obvious stratification phenomenon, and the instantaneous sample solvent water content is measured to be 1103ppm. After the reaction is kept at this temperature for 6 hours, the instantaneous sample solvent water content is measured to be 753.6ppm, and the reaction is stopped.

[0039] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0040] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the temperature is cooled to room temperature, 800g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is cooled to -5°C for crystallization. After the filtrate is filtered, 295g of powdery lithium perchlorate wet material is obtained.

[0041] E. The wet material obtained by filtering in step D was vacuum dried at a vacuum pressure of 500 mmHg and a drying temperature of 120° C. for 10 h to obtain 216 g of white powdery crystals with a yield of 88.6%. The moisture content was 143.5 ppm and the IC purity was 99.9%.

[0042] Example 4

[0043] A method for preparing high-purity and low-water content lithium perchlorate comprises the following steps:

[0044] A. Take 100g of lithium hydroxide monohydrate and add it into a three-necked flask (equipped with a condenser and a water separator) containing a mixed solvent of 600g of diethyl carbonate and 200g of chlorobenzene. Start stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0045] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. The reaction liquid becomes clear at about 60°C and the temperature is continuously raised to 150°C. When the temperature is kept at 150°C for 4.5 hours, the separated solvent has no obvious stratification phenomenon and the instantaneous sample solvent water content is 1213 ppm. After the reaction is kept at this temperature for 6 hours, the instantaneous sample solvent water content is 593.2 ppm and the reaction is stopped.

[0046] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0047] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the temperature is cooled to room temperature, 800g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is cooled to -5°C for crystallization. After the filtrate is filtered, 296g of wet powdery lithium perchlorate is obtained.

[0048] E. The wet material obtained by filtering in step D was vacuum dried, the vacuum pressure was set to 500 mmHg, the drying temperature was 120° C., and the drying was performed for 12 h to obtain 216 g of white powdery crystals with a yield of 88.6%. The moisture value was measured to be 106.7 ppm, and the IC purity was 99.9%.

[0049] Example 5

[0050] A method for preparing high-purity and low-water content sodium perchlorate comprises the following steps:

[0051] A. Take 91.74g of sodium hydroxide and add it to a three-necked flask (equipped with a condenser and a water separator) containing a mixed solvent of 600g of ethyl methyl carbonate and 200g of chlorobenzene. Turn on stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0052] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. The reaction liquid becomes clear at about 60°C. The temperature is continuously raised to 130°C, and the solvent is stably separated. When the temperature is kept at 130°C for 5 hours, the separated solvent has no obvious stratification phenomenon, and the instantaneous sample solvent water content is measured to be 1103ppm. After the reaction is kept at this temperature for 6 hours, the instantaneous sample solvent water content is measured to be 505.2ppm, and the reaction is stopped.

[0053] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0054] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the temperature is cooled to room temperature, 800g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is cooled to -5°C for crystallization. After the filtrate is filtered, 296g of powdered sodium perchlorate wet material is obtained.

[0055] E. The wet material obtained by filtering in step D was vacuum dried, the vacuum pressure was set to 500 mmHg, the drying temperature was 120° C. and the drying was performed for 12 h to obtain 259.6 g of white powdery crystals with a yield of 92.6%. The moisture value was measured to be 85.3 ppm and the IC purity was 99.9%.

[0056] Comparative Example 1

[0057] A method for preparing high-purity and low-water content lithium perchlorate comprises the following steps:

[0058] A. Take 100g of lithium hydroxide monohydrate and add it into a three-necked flask (equipped with a condenser and a water separator) containing 800g of diethyl carbonate, start stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0059] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. The reaction liquid becomes clear at about 60°C and the temperature is continuously raised to 130°C. When the reaction is maintained at 130°C for 6.5 hours, it is observed that there is no obvious stratification of the separated solvent. The instantaneous sample solvent water content is 5151ppm. After the reaction is maintained at 130°C for 7 hours, the instantaneous sample solvent water content is 3893ppm. After the reaction is maintained at 12 hours, the instantaneous sample solvent water content is 2913ppm. After the reaction is maintained at 17 hours, the instantaneous sample solvent water content is 1892ppm. After the reaction is maintained at 24 hours, the instantaneous sample solvent water content is 883ppm. The reaction is stopped.

[0060] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0061] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the temperature is cooled to room temperature, 800g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is cooled to -5°C for crystallization. After the filtrate is filtered, 206.3g of powdery lithium perchlorate wet material is obtained.

[0062] E. The wet material obtained by filtering in step D was vacuum dried, the vacuum pressure was set to 500 mmHg, the drying temperature was 120° C. and the drying was performed for 12 h to obtain 185.8 g of white powdery crystals with a yield of 76.2%. The moisture value was measured to be 123.6 ppm and the IC purity was 99.9%.

[0063] Comparative Example 2

[0064] A method for preparing high-purity and low-water content lithium perchlorate comprises the following steps:

[0065] A. Take 100g of lithium hydroxide monohydrate and add it into a three-necked flask (equipped with a condenser and a water separator) containing 800g of diethyl carbonate, start stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0066] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. The reaction liquid becomes clear at about 60°C and the temperature is continuously raised to 130°C. When the reaction is continued at 130°C for 6.5 hours, it is observed that there is no obvious stratification of the separated solvent. The instantaneous sample solvent water content is 5155ppm. After the reaction is kept warm for 7 hours, the instantaneous sample solvent water content is 3896ppm. After the reaction is kept warm for 22 hours, the instantaneous sample solvent water content is 1336ppm, and the reaction is stopped.

[0067] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0068] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the temperature is cooled to room temperature, 800g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is cooled to -5°C for crystallization. After the filtrate is filtered, 205.3g of powdery lithium perchlorate wet material is obtained.

[0069] E. The wet material filtered in step D was vacuum dried at a vacuum pressure of 500 mmHg and a drying temperature of 120° C. for 12 h to obtain 184.87 g of white powdery crystals with a yield of 75.8%. The moisture content was 356 ppm and the IC purity was 99.5%.

[0070] Comparative Example 3

[0071] A method for preparing high-purity and low-water content sodium perchlorate comprises the following steps:

[0072] A. Take 91.74g of sodium hydroxide and add it to a three-necked flask (equipped with a condenser and a water separator) containing 800g of ethyl methyl carbonate, start stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0073] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. The reaction liquid becomes clear at about 60°C and the temperature is continuously raised to 130°C. After the reaction is continued at 130°C for 21 hours, it is observed that there is no obvious stratification of the separated solvent. The instantaneous sample solvent water content is 2315 ppm. After the reaction is kept at this temperature for 23.5 hours, the instantaneous sample solvent water content is 583.2 ppm, and the reaction is stopped.

[0074] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0075] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the temperature is cooled to room temperature, 800g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is cooled to -5°C for crystallization. After the filtrate is filtered, 296g of powdered sodium perchlorate wet material is obtained.

[0076] E. The wet material obtained by filtering in step D was vacuum dried, the vacuum pressure was set to 500 mmHg, the drying temperature was 120° C. and the drying was performed for 12 h to obtain 257.95 g of white powdery crystals with a yield of 92%. The moisture value was measured to be 113.8 ppm and the IC purity was 99.9%.

[0077] Comparative Example 4

[0078] A method for preparing high-purity and low-water content sodium perchlorate comprises the following steps:

[0079] A. Take 91.74g of sodium hydroxide and add it to a three-necked flask (equipped with a condenser and a water separator) containing 800g of ethyl methyl carbonate, start stirring, and then slowly add 320g of 72wt% perchloric acid dropwise at room temperature (25°C) for 1.5h.

[0080] B. Dehydration reaction: After the addition of perchloric acid is completed, the temperature begins to rise. The reaction liquid becomes clear at about 60°C and the temperature is continuously raised to 130°C. When the temperature is kept at 130°C for 6 hours, the separated solvent has no obvious stratification phenomenon and the instantaneous sample solvent water content is 5893 ppm. When the temperature is kept at 130°C for 21 hours, the instantaneous sample solvent water content is 1431 ppm and the reaction is stopped.

[0081] C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is naturally cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities.

[0082] D. Concentration and crystallization: The filtrate filtered in step C above is concentrated under reduced pressure to remove excess solvent, and the oil bath temperature is set to 80°C and the vacuum pressure is -0.09MPa. After crystals are precipitated, the heating is stopped, and after the temperature is cooled to room temperature, 800g of chlorobenzene is slowly added dropwise to the filtrate, and then the temperature is cooled to -5°C for crystallization. After the filtrate is filtered, 290g of powdered sodium perchlorate wet material is obtained.

[0083] E. The wet material obtained by filtering in step D was vacuum dried, the vacuum pressure was set to 500 mmHg, the drying temperature was 120° C. and the drying was performed for 12 h to obtain 250.9 g of white powdery crystals with a yield of 89.5%. The moisture value was measured to be 406 ppm and the IC purity was 99.6%.

[0084] From the above results, it can be seen that when lithium hydroxide monohydrate / sodium hydroxide and perchloric acid are used as reaction raw materials and a single ester solvent is selected for water separation and water removal, it takes 20-24 hours for the instantaneous sample water content to be less than 1000ppm, while the mixed solvent system of ester solvents and benzene solvents is used for water separation and water removal, and the time for the instantaneous sample to be less than 1000ppm is shortened to 6-8h. In addition, the mixed solvent system of ester solvents and benzene solvents is used for water separation and water removal, and the yield of the target product is more than 85%, the purity is more than 99.8%, and the water content is less than 200ppm.

Claims

1. A method for preparing high-purity and low-water perchlorate, characterized in that: The following steps are involved: A. adding lithium hydroxide monohydrate into a reactor containing a mixed solvent of an ester solvent and a benzene solvent, wherein the reactor is equipped with a condenser and a water separator for subsequent dehydration; B. Dehydration reaction: at room temperature, under magnetic stirring, slowly add 70wt%-73wt% perchloric acid to the mixed solution of step A, the molar ratio of lithium hydroxide monohydrate in the system to the added perchloric acid is 1-1.05:1, and the dripping is completed in 1.5-2h. After the dripping is completed, heat to 120-150°C and keep warm for 6-8h. Stop the reaction when the instantaneous solvent water separated from the reaction system does not exceed 1000ppm; C. Filtration and impurity removal: After the dehydration reaction is completed, the reaction solution is cooled to room temperature under nitrogen protection, and then the reaction solution is filtered to remove insoluble impurities; D. Concentration and crystallization: The filtrate filtered in the above step C is concentrated under reduced pressure at a vacuum pressure of -0.08 to -0.1 MPa and a temperature of 50-130° C. to remove excess solvent. After crystals are precipitated, heating is stopped, and after cooling to room temperature, a poor solvent for perchlorate is slowly added dropwise to the concentrated filtrate, followed by cooling for crystallization at a cooling temperature of -5-5° C. The filtrate is filtered to obtain a wet material; E. vacuum drying the wet material obtained by filtration in step D to obtain lithium perchlorate crystals with a purity of more than 99.8% and a moisture value of less than 200 ppm; Alternatively, in step A, the lithium hydroxide monohydrate is replaced by sodium hydroxide, and finally in step E, sodium perchlorate crystals are obtained, the purity of the sodium perchlorate is above 99.8%, and the moisture value is less than 200 ppm.

2. The preparation method according to claim 1, characterized in that: The ester solvent is a mixture of one or more of ethyl acetate, isopropyl acetate, methyl propionate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, and ethylene carbonate; the benzene solvent is a mixture of one or more of toluene, o-xylene, m-xylene, chlorobenzene, and p-xylene.

3. The preparation method according to claim 1, characterized in that: In the mixed solvent, the mass ratio of the ester solvent to the benzene solvent is 4:1-4, preferably 3:1-2; and / or The mass ratio of lithium hydroxide monohydrate to the mixed solvent is 1:6-11, preferably 1:7.5-9.

4. The preparation method according to claim 1, characterized in that: In step D, the poor solvent is a mixture of one or more of dichloromethane, dichloroethane, 1-chloropropane, toluene, chlorobenzene, n-heptane, and cyclohexane. Preferably, the amount of the poor solvent added is 3-6 times the mass of the theoretical target product.

5. The preparation method according to claim 1, characterized in that: In step E, the vacuum drying conditions are: drying temperature is 100-130° C., drying time is 6-12 h, and vacuum pressure is 200-1000 mmHg.