阅读说明：本技术 一种利用氯气制备氯化锂的方法 (Method for preparing lithium chloride by using chlorine ) 是由 洪侃 于 2019-10-15 设计创作，主要内容包括：本发明公开一种利用氯气制备氯化锂的方法,将氯气与氢氧化锂溶液反应得到次氯酸锂溶液后,再依次加入氯化铵、双氧水,经蒸发结晶即得氯化锂。本发明首次提出了氯气制备氯化锂的分步工序,通过理论计算,将反应吉布斯自由能较小、易反应的氯化铵先加入溶液中,将溶液中大部分次氯酸锂转化；随后又加入反应限度高的双氧水二次氯化,既解决了氯化铵制备氯化锂纯度不高的缺陷,又降低了双氧水制备氯化锂用量大、成本高等问题,有着不引人新的杂质,所得氯化锂纯度高等优点。(The invention discloses a method for preparing lithium chloride by using chlorine, which comprises the steps of reacting the chlorine with a lithium hydroxide solution to obtain a lithium hypochlorite solution, sequentially adding ammonium chloride and hydrogen peroxide, and evaporating and crystallizing to obtain the lithium chloride. The invention provides a step procedure for preparing lithium chloride by chlorine for the first time, and through theoretical calculation, ammonium chloride which has small Gibbs free energy and is easy to react is firstly added into a solution, and most of lithium hypochlorite in the solution is converted; and then hydrogen peroxide with high reaction limit is added for secondary chlorination, so that the defect of low purity of lithium chloride prepared by ammonium chloride is overcome, the problems of large using amount, high cost and the like of lithium chloride prepared by hydrogen peroxide are solved, and the method has the advantages of no introduction of new impurities, high purity of the obtained lithium chloride and the like.)

1. A method for preparing lithium chloride by using chlorine gas is characterized in that: and reacting chlorine gas with a lithium hydroxide solution to obtain a lithium hypochlorite solution, sequentially adding ammonium chloride and hydrogen peroxide, and evaporating and crystallizing to obtain the lithium chloride.

2. The method for preparing lithium chloride by using chlorine gas as claimed in claim 1, wherein: the chlorine gas is high-temperature chlorine gas generated by electrolyzing and melting lithium chloride, and is cooled to the temperature of less than or equal to 35 ℃.

3. The method for preparing lithium chloride by using chlorine gas as claimed in claim 1, wherein: the mol ratio of the chlorine gas to the lithium hydroxide in the lithium hydroxide solution is 1: 2.0 to 2.4, and the concentration of the lithium hydroxide solution is 50 to 100 g/L.

4. The method for preparing lithium chloride by using chlorine gas as claimed in claim 1, wherein: the molar ratio of the added amount of the ammonium chloride to the lithium hypochlorite in the lithium hypochlorite solution is 0.01-0.04: 1, the reaction time is 10-30 min.

5. The method for preparing lithium chloride by using chlorine gas as claimed in claim 1, wherein: the molar ratio of the added hydrogen peroxide to the lithium hypochlorite in the lithium hypochlorite solution is 0.008-0.016: 1, the reaction time is 10-30 min, and the mass fraction of the hydrogen peroxide is 30%.

6. A process for preparing lithium chloride from chlorine as claimed in any of claims 1 to 5, wherein: the purity of the lithium chloride is not lower than 99.0%.

Technical Field

The invention relates to a preparation method of lithium chloride, in particular to a method for preparing anhydrous lithium chloride by utilizing a large amount of pure chlorine generated by preparing metal by electrolyzing molten chloride, belonging to the field of chemical raw material preparation.

Background

Lithium chloride is increasingly demanded as a raw material for preparing metal lithium, a welding agent for metal alloy, a dehumidifying agent for air conditioner, a raw material for pharmaceutical industry and special cement, etc. The preparation method mainly comprises the following three methods: (1) the method adopts lithium hydroxide or lithium carbonate and hydrochloric acid to react to generate lithium chloride, and obtains anhydrous lithium chloride products after the procedures of separation, washing, concentration, crystallization, drying and the like; the method has the defects that the process needs to be subjected to the working procedures of washing, concentration and the like for many times, and the energy waste is large; (2) the direct conversion method of ore, said method regards spodumene concentrate as raw materials, convert spodumene concentrate into lithium sulfate at first, make lithium hydroxide or lithium carbonate from lithium sulfate, prepare anhydrous lithium chloride through the method (1) finally; the method has the disadvantages of long process flow, multiple operation procedures, large equipment investment and easy loss of lithium; (3) the method for extracting and producing lithium chloride from salt lake lithium ore comprises the process steps of acidification reaction, purification and impurity removal, chlorination reaction, freezing sodium precipitation, concentration lithium precipitation and the like.

At present, most of lithium metal production adopts an electrolytic melting lithium chloride electrolytic process, a large amount of pure chlorine gas can be generated, and in order to realize the problems of chlorine gas recycling, chlorine gas pollution and the like in industry, lithium hydroxide is generally used for absorbing chlorine gas to prepare lithium chloride, for example, as indicated in the text of research progress of application and production methods of lithium chloride published by Qinghai lake research institute of Chinese academy of sciences: lithium hydroxide and chlorine can be directly chloridized to prepare lithium chloride; the Ganxfeng lithium industry published 'technical method for producing lithium chloride by recycling electrolytic lithium metal chlorine', the text also indicates that: the preparation of lithium chloride from chlorine gas in the lithium hydroxide recovery and electrolysis process is feasible under the promotion of a catalyst. However, in the related reports published at present, lithium hypochlorite generated by absorbing chlorine gas by lithium hydroxide still belongs to the problem difficult to treat in the industry, although the problem of the lithium hypochlorite can be solved to a certain extent by adopting a catalyst, the added catalyst is usually ferric salt, nickel salt and the like, and excessive catalyst introduces impurities such as iron, nickel and the like, so that the impurities of the lithium chloride are easy to exceed the standard and the electrolysis cannot be carried out; the addition amount of the catalyst is small, hypochlorite cannot be fully treated, and further the production of lithium chloride by evaporation crystallization is a trough, so that certain potential safety hazard exists, and therefore, a safe and efficient process for preparing lithium chloride by chlorine is urgently needed to be developed.

Disclosure of Invention

In order to solve the defects of the existing chlorine recovery and lithium chloride preparation process, the invention aims to provide a method for preparing lithium chloride by using chlorine, firstly provides a step procedure for preparing lithium chloride by using chlorine, and firstly adds ammonium chloride which has small Gibbs reaction free energy and is easy to react into a solution by theoretical calculation to convert most of lithium hypochlorite in the solution; and then hydrogen peroxide with high reaction limit is added for secondary chlorination, so that the defect of low purity of lithium chloride prepared by ammonium chloride is overcome, the problems of large using amount, high cost and the like of lithium chloride prepared by hydrogen peroxide are solved, and the method has the advantages of no introduction of new impurities, high purity of the obtained lithium chloride and the like.

In order to achieve the technical purpose, the invention provides a method for preparing lithium chloride by using chlorine, which comprises the steps of reacting the chlorine with a lithium hydroxide solution to obtain a lithium hypochlorite solution, sequentially adding ammonium chloride and hydrogen peroxide, and evaporating and crystallizing to obtain the lithium chloride.

Preferably, the chlorine gas is high-temperature chlorine gas generated by electrolyzing and melting lithium chloride, and the chlorine gas is cooled to the temperature of less than or equal to 35 ℃.

Preferably, the molar ratio of the chlorine gas to the lithium hydroxide in the lithium hydroxide solution is 1: 2.0 to 2.4, and the concentration of the lithium hydroxide solution is 50 to 100 g/L.

When the invention uses the high-temperature chlorine generated by electrolyzing and melting the lithium chloride as the raw material, the chlorine is introduced into the excessive lithium hydroxide solution, thereby avoiding the generation of the excessive chlorine, realizing the zero emission of the chlorine and meeting the requirement of environmental-friendly production.

Preferably, the molar ratio of the added amount of the ammonium chloride to the lithium hypochlorite in the lithium hypochlorite solution is 0.01-0.04: 1, the reaction time is 10-30 min.

Preferably, the molar ratio of the added hydrogen peroxide to the lithium hypochlorite in the lithium hypochlorite solution is 0.008-0.016: 1, the reaction time is 10-30 min, and the mass fraction of the hydrogen peroxide is 30%.

The method utilizes chlorine generated by lithium chloride electrolysis to prepare lithium chloride, and introduces the chlorine into excessive lithium hydroxide solution, thereby avoiding the generation of excessive chlorine and realizing the recycling of the chlorine, thereby realizing zero emission of the chlorine and meeting the requirement of green production; in the process of preparing lithium chloride, the inventor researches and discovers that both ammonium chloride and hydrogen peroxide can effectively catalyze lithium hypochlorite to decompose into lithium chloride and oxygen, and simultaneously can react with the lithium hypochlorite to convert hypochlorite into chloride, and calculates the Gibbs free energy of the reaction of the ammonium chloride, the hydrogen peroxide and the lithium hypochlorite. This phenomenon is also confirmed in subsequent experiments, and in the experiments, the inventors found that, under the condition of coexistence of ammonium chloride and hydrogen peroxide, hydrogen peroxide can be decomposed into water and oxygen in a very short time because hydrogen peroxide does not participate in chlorination reaction of hypochlorous acid; the inventor also finds in experiments that the limit of conversion of hydrogen peroxide to lithium hypochlorite is higher than that of ammonium chloride, so in order to save reagent cost and improve conversion, the invention provides a process for chlorination treatment of lithium hypochlorite step by adding ammonium chloride first and then hydrogen peroxide. The invention converts lithium hypochlorite in lithium hydroxide absorption liquid into lithium chloride to the maximum extent, and the reaction equation is as follows:

Cl₂+2LiOH＝LiClO+LiCl+H₂O

2LiClO＝2LiCl+O₂(g)

3LiClO+2NH₄Cl＝3LiCl+N₂(g)+3H₂O+3HCl

H₂O₂+LiClO＝LiCl+H₂O+O₂(g)

compared with the existing lithium hypochlorite treatment process, the method has the advantages that new impurities cannot be introduced by using ammonium chloride and hydrogen peroxide to chlorinate lithium hypochlorite, the fractional catalytic treatment efficiency is high, and the purity of the obtained lithium chloride is high and can be not lower than 99.0%.

Compared with the prior art, the invention has the advantages that:

1. when high-temperature chlorine generated by electrolyzing and melting lithium chloride is used as a raw material, the chlorine is introduced into the excessive lithium hydroxide solution, so that the generation of the excessive chlorine is avoided, and the recycling of the chlorine is realized, so that the zero emission of the chlorine can be realized, and the requirement of green production is met;

2. according to the invention, the research on the chlorination efficiency in the preparation of lithium chloride is firstly carried out, the step procedure of preparing lithium chloride by chlorine is firstly provided, and by theoretical calculation, ammonium chloride which has small Gibbs free energy and is easy to react is firstly added into the solution, and most of lithium hypochlorite in the solution is converted; then adding hydrogen peroxide with high reaction limit for secondary chlorination. The invention not only solves the defect of low purity of the lithium chloride prepared by ammonium chloride, but also reduces the problems of large using amount, high cost and the like of the lithium chloride prepared by hydrogen peroxide by standardizing the adding sequence of the ammonium chloride and the hydrogen peroxide in the step-by-step process.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention.