Purification method of electronic-grade lithium chloride

Abstract

The invention discloses a method for purifying electronic-grade lithium chloride, which comprises the following steps of: separating solid impurities by water dissolution, removing low-melting-point impurities by low-temperature boiling, filtering out impurity precipitates and impurity solution by various chemical reactions, and purifying by repeated acid-alkali treatment to finally obtain the electronic-grade lithium chloride with the purity not lower than 8N grade. The method has the characteristics of good purification effect, multi-method comprehensive impurity removal, industrial large-scale application, stable quality, high yield and simple and easy-to-separate impurity components.

Description

Technical Field

[0001] The present invention relates to a high-purity semiconductor dopant, and in particular to a method for purifying electronic-grade lithium chloride. Background Art

[0002] Doping of semiconductors is to improve the electrical properties of semiconductor devices, and many electrical characteristics of semiconductors are related to the impurity concentration of doping.

[0003] Lithium chloride has a wide range of application fields. Among them, the purity above 5N level (impurity content not higher than 0.001%) can be used as a precursor in the fields of semiconductors, ultra-high temperature ceramics, high-power LEDs, atomic reactors, etc. In recent years, driven by the rapid development of the downstream market, the market demand for lithium chloride has been increasing continuously, and the demand space is relatively broad. However, there are obvious shortcomings in the output and technology of high-purity lithium chloride (electronic-grade lithium chloride) in China.

[0004] The existing high-purity anhydrous lithium chloride in the prior art must be refined and purified. There are three common refining methods: (1) sublimation after acidification with carbonate; (2) converting lithium fluoride precipitate into lithium chloride; (3) refining with ion exchange resin.

[0005] In the current prior art, there is no related technology to solve the above problems. At present, a purification method for electronic-grade lithium chloride with good purification effect, comprehensive impurity removal by multiple methods, industrial-scale application, stable quality, and high yield is needed. Summary of the Invention

[0006] The present invention aims to provide a purification method for electronic-grade lithium chloride with good purification effect, comprehensive impurity removal by multiple methods, industrial-scale application, stable quality, high yield, and simple and easy separation of impurity components.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A purification method for electronic-grade lithium chloride, the purification method includes the following stages: S1: Raw material preparation ① Raw material preparation: Prepare sufficient industrial lithium carbonate, saturated aqueous solution of calcium hydroxide, deionized water, hydrochloric acid aqueous solution with a solute mass fraction of 1%, ammonium bicarbonate aqueous solution with a solute mass fraction of 10%, and ethanol; ② Tooling and equipment preparation: Prepare a water bath constant temperature device, a vacuum chamber with a vacuum degree of 1×10 -4 Pa~10 Pa, and a quartz encapsulation container; S2: Pretreatment ① After completely dissolving the lithium carbonate prepared in step ① of stage S1 with deionized water, filter to retain the solid content, and then dry the solid content to obtain roughly purified lithium carbonate; ② Heat the crudely purified lithium carbonate obtained in step ① to 270°C - 340°C first. After the low-boiling impurities have volatilized until the mass is stable, obtain the preliminarily purified lithium carbonate. ③ Mix deionized water and the preliminarily purified lithium carbonate prepared in step ② evenly at a mass ratio of (18 - 22):1. Then, dropwise add the saturated aqueous solution of calcium hydroxide prepared in step ① of stage S1 into the mixture until no new precipitate is produced in the reaction system. Filter out the solid content and retain the solution to obtain the crude lithium hydroxide solution. ④ In the crude lithium hydroxide solution obtained in step ③, introduce carbon dioxide prepared in step ① of stage S1 into the reaction system at a rate of 0.2 L / min - 0.3 L / min while maintaining the temperature of the reaction system not higher than 15°C until no more precipitate is produced. Filter the liquid and retain the solid content. Wash the solid content repeatedly 2 - 3 times with ethanol prepared in step ① of stage S1. After drying, obtain 5N-grade lithium carbonate. S3: Acidification and alkali neutralization purification ① Place the 5N-grade lithium carbonate obtained in step ④ of stage S2 in the vacuum chamber prepared in step ② of stage S1. Continuously evacuate to maintain the vacuum degree and uniformly inject the hydrochloric acid aqueous solution prepared in step ① of stage S1 until the mass of the solid content no longer changes and no more gas is produced. Filter out the solid content to obtain the acidified lithium chloride aqueous solution. ② Slowly dropwise add the aqueous solution of ammonium bicarbonate prepared in step ① of stage S1 into the acidified lithium chloride aqueous solution obtained in step ① until no more precipitate is produced. Filter out the precipitate and wash the precipitate repeatedly 2 - 3 times with ethanol prepared in step ① of stage S1 to obtain the pre-purified lithium carbonate. Then, heat the washed precipitate to 270°C - 340°C until the mass no longer changes to obtain the secondarily purified lithium carbonate. ③ Place the secondarily purified lithium carbonate obtained in step ② in the vacuum chamber prepared in step ② of stage S1. Continuously evacuate to maintain the vacuum degree and uniformly inject the hydrochloric acid aqueous solution prepared in step ① of stage S1 until no more gas is produced. Heat the mixture until crystallization is stable, filter out the crystals, wash the crystals repeatedly 2 - 3 times with ethanol prepared in step ① of stage S1, and then heat the washed precipitate to 270°C - 340°C until the mass no longer changes to obtain the secondarily purified lithium chloride. S4: Detection ① Detect the secondarily purified lithium chloride obtained in step ③ of stage S3. The requirements are that the impurity content is not higher than 0.000001%, the moisture content is not greater than 2 ppm, and the lithium chloride content is not lower than 99.95% to obtain the target lithium chloride. S5: Encapsulation ① Encapsulate the lithium chloride that has passed the detection in step ① of stage S4 in the vacuum chamber prepared in step ② of stage S1 using the quartz encapsulation container prepared in step ② of stage S1. After encapsulation and sealing, obtain the required electronic-grade lithium chloride.

[0008] Compared with the prior art, due to the adoption of the above technical solutions, the present invention has the following advantages: (1) The lithium chloride purification technology used in the present invention is different from general purification technologies and can complement the existing commonly used technologies. Its main function is to utilize the physical properties of lithium chloride, and use the chemical properties of lithium chloride and the solubility changes of various chemical conversion products with water for staggered purification, which is particularly suitable for purification after crude distillation. The purification method adopted by the present invention not only has simple process conditions, low energy consumption, simple equipment, low equipment maintenance frequency, short cycle period, and no special requirements for raw materials, but also has very good comprehensive purification effects. Moreover, the physical purification of the present invention can also be combined with the molecular sieve adsorption method and other methods not applied in the present invention, and the purification effects are complementary.

[0009] (2) For the physical pre-purification of the present invention, after removing solids by water dissolution and then removing low-melting-point impurities by low-temperature distillation, high-melting-point substances are removed by high-temperature sublimation under vacuum conditions. Only through the pretreatment, a purity of 5N (purity not lower than 99.999%) can be obtained, and this condition already meets the requirements of the 14nm manufacturing process.

[0010] Therefore, the present invention has the characteristics of good purification effect, comprehensive impurity removal by multiple methods, industrial-scale application, stable quality, high yield, and simple impurity components and easy separation. Specific embodiments Example 1

[0011] A purification method for electronic-grade lithium chloride, which includes the following stages: S1: Raw material preparation ① Raw material preparation: Prepare sufficient industrial lithium carbonate, saturated aqueous solution of calcium hydroxide, deionized water, hydrochloric acid aqueous solution with a solute mass fraction of 1%, ammonium bicarbonate aqueous solution with a solute mass fraction of 10%, and ethanol; ② Tooling and equipment preparation: Prepare a water bath constant temperature device, a vacuum chamber with a vacuum degree of 1×10 -4 Pa~10 Pa, and a quartz encapsulation container; S2: Pretreatment ① After completely dissolving the lithium carbonate prepared in step ① of stage S1 with deionized water, filter to retain the solid content, and then dry the solid content to obtain crudely purified lithium carbonate; ② First heat the crudely purified lithium carbonate obtained in step ① to 270°C~340°C, and wait until the low-boiling-point impurities volatilize to a stable mass to obtain initially purified lithium carbonate; ③ Mix deionized water and the initially purified lithium carbonate prepared in step ② in a mass ratio of (18~22):1, and then immediately add the saturated aqueous solution of calcium hydroxide prepared in step ① of stage S1 to the mixture until no new precipitate is generated in the reaction system. Filter to remove the solid content and retain the solution to obtain a crude lithium hydroxide solution; ④In the crude lithium hydroxide solution obtained in step ③, carbon dioxide prepared in step ① of stage S1 is introduced at a rate of 0.2 L / min to 0.3 L / min, while maintaining the temperature of the reaction system not higher than 15 °C until no more precipitation occurs. Then, the liquid is filtered to retain the solid content, and the solid content is repeatedly washed 2 to 3 times with ethanol prepared in step ① of stage S1. After drying, 5N grade lithium carbonate is obtained; S3: Acidification and alkali neutralization purification ①Put the 5N grade lithium carbonate obtained in step ④ of stage S2 into the vacuum chamber prepared in step ② of stage S1. Continuously evacuate to maintain the vacuum degree, and uniformly inject the hydrochloric acid aqueous solution prepared in step ① of stage S1 until the mass of the solid content no longer changes and no more gas is generated. Then, filter out the solid content to obtain the acidified lithium chloride aqueous solution; ②Slowly drop the ammonium bicarbonate aqueous solution prepared in step ① of stage S1 into the acidified lithium chloride aqueous solution obtained in step ① until no more precipitation occurs. Filter out the precipitate, and repeatedly wash the precipitate 2 to 3 times with ethanol prepared in step ① of stage S1 to obtain pre-purified lithium carbonate. Then, heat the washed precipitate to 270 °C to 340 °C until the mass no longer changes, and obtain secondary purified lithium carbonate; ③Put the secondary purified lithium carbonate obtained in step ② into the vacuum chamber prepared in step ② of stage S1. Continuously evacuate to maintain the vacuum degree, and uniformly inject the hydrochloric acid aqueous solution prepared in step ① of stage S1 until no more gas is generated. Heat the mixture to the crystallization stability, filter out the crystals, and repeatedly wash the crystals 2 to 3 times with ethanol prepared in step ① of stage S1. Then, heat the washed precipitate to 270 °C to 340 °C until the mass no longer changes, and obtain secondary purified lithium chloride; S4: Detection ①Detect the secondary purified lithium chloride obtained in step ③ of stage S3. It is required that the impurity content is not higher than 0.000001%, the moisture content is not more than 2 ppm, and the lithium chloride content is not less than 99.95% to obtain the target lithium chloride; S5: Encapsulation ①Encapsulate the lithium chloride qualified in step ① of stage S4 in the vacuum chamber prepared in step ② of stage S1 using the quartz encapsulation container prepared in step ② of stage S1. After encapsulation and sealing, the required electronic grade lithium chloride is obtained.

[0012] The electronic grade lithium chloride obtained according to this embodiment has the characteristics of good purification effect, comprehensive impurity removal by multiple methods, applicable to industrial scale, stable quality, high yield, and simple impurity components easy to separate.

[0013] The above description of the disclosed embodiments is only to enable those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for purifying electronic grade lithium chloride, characterized in that: The purification method The following phases are included: S1: Raw material preparation ① Raw material preparation: prepare sufficient industrial lithium carbonate, saturated calcium hydroxide aqueous solution, deionized water, 1% hydrochloric acid aqueous solution, 10% ammonium bicarbonate aqueous solution, and ethanol; ② Preparation of tools and equipment: prepare a water bath thermostat with a vacuum degree of 1×10 -4 Pa~10Pa vacuum chamber, quartz packaging container; S2: Preprocessing ① using deionized water to completely dissolve the lithium carbonate prepared in step ① of stage S1, then filtering and retaining the solid content, and then drying the solid content to obtain crude purified lithium carbonate; ② The crude purified lithium carbonate obtained in step ① is first heated to 270° C. to 340° C., and after the low-boiling impurities are volatilized to a stable quality, the initially purified lithium carbonate is obtained; ③ Deionized water and the initially purified lithium carbonate prepared in step ② are mixed uniformly in a mass ratio of (18-22):1, and then the saturated aqueous solution of calcium hydroxide prepared in step ① of stage S1 is added dropwise to the mixture until no new precipitate is generated in the reaction system, and the solid content is filtered out and the solution is retained to obtain a crude lithium hydroxide solution; ④ Into the crude lithium hydroxide solution obtained in step ③, the carbon dioxide prepared in step ① of stage S1 is introduced at a rate of 0.2 L / min to 0.3 L / min, while maintaining the temperature of the reaction system not higher than 15° C. until no precipitation is generated, the liquid is filtered, the solid content is retained, and the solid content is repeatedly washed 2 to 3 times with ethanol prepared in step ① of stage S1, and 5N grade lithium carbonate is obtained after drying; S3: Acidification and alkali neutralization and purification ① Place the 5N lithium carbonate obtained in step ④ of stage S2 in the vacuum chamber prepared in step ② of stage S1, continue to evacuate and maintain the vacuum degree, uniformly inject the hydrochloric acid aqueous solution prepared in step ① of stage S1 until the mass of the solid content no longer changes and the gas no longer generates, filter out the solid content, and obtain an acidified lithium chloride aqueous solution; ② Slowly drop the ammonium bicarbonate aqueous solution prepared in step S1① into the acidified lithium chloride aqueous solution obtained in step ① until no precipitation is generated, filter out the precipitate, and repeatedly wash the precipitate with the ethanol prepared in step S1① for 2 to 3 times to obtain pre-purified lithium carbonate, and then heat the washed precipitate to 270° C. to 340° C. until the mass no longer changes, thereby obtaining secondary purified lithium carbonate; ③ Place the secondary purified lithium carbonate obtained in step ② in the vacuum chamber prepared in step ② of stage S1, continuously evacuate to maintain the vacuum degree, uniformly inject the hydrochloric acid aqueous solution prepared in step ① of stage S1 until gas is no longer generated, heat the mixed solution until the crystals are stable, filter out the crystals, and repeatedly wash the crystals with ethanol prepared in step ① of stage S1 for 2 to 3 times, and then heat the washed precipitate to 270° C. to 340° C. until the mass no longer changes, thereby obtaining secondary purified lithium chloride; S4: Detection ① Testing the secondary purified lithium chloride obtained in step ③ of stage S3, requiring the impurity content to be no higher than 0.000001%, the water content to be no greater than 2 ppm, and the lithium chloride content to be no less than 99.95%, to obtain the target lithium chloride; S5: Encapsulation ① The qualified lithium chloride detected in step ① of stage S4 is packaged in the vacuum chamber prepared in step ② of stage S1 using the quartz packaging container prepared in step ② of stage S1. After the packaging is completed and sealed, the required electronic grade lithium chloride is obtained.