JPH0416406B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying lithium fluoride complex salts, and the high purity lithium fluoride complex salts obtained by the method of the present invention can be used as electrolytes in high-energy batteries and as catalysts in organic synthesis reactions. It is industrially important as a catalyst in polymerization reactions, a doping agent for semiconductor materials, or as a raw material for these materials.

The present inventors have conducted numerous studies on purification methods for lithium fluoride complex salts, but the biggest drawback in using them for the above-mentioned purposes is that lithium fluoride complex salts are highly hygroscopic, and due to the manufacturing process, The problem was that the quality deteriorated due to water and other impurities introduced during storage and handling. The moisture content varies depending on the operating conditions, but when the crude lithium fluoride complex salt is a solid such as crystal, lump, or powder, it is approximately 0.05 to 10.00.
% of water in the form of crystallization water or adhering water, which is an abominable disadvantage when used in various applications.

Here, the present inventors have developed a remarkable new method for producing a highly purified lithium fluoride complex salt.

That is, the present inventors brought a crude complex salt with a structure consisting of a fluoride of a group 3 to 5 element of the periodic table and lithium fluoride into contact with fluorine at -10 to +100°C in an inert gas. They have discovered that lithium fluoride complex salts can be purified easily and economically.

Fluorides of elements from groups 3 to 5 of the periodic table include boron,
It is a fluoride of silicon, titanium, zirconium, germanium, tin, phosphorus, vanadium, arsenic, niobium, antimony, tantalum, and bismuth, singly or as a mixture. These include boron fluoride, titanium fluoride, zirconium fluoride, tin fluoride, phosphorus fluoride, arsenic fluoride, and antimony fluoride. There are various kinds of complex salts with structures consisting of fluorides of Groups 3 to 5 elements of the periodic table and lithium fluoride. Among them, representative ones include boron, titanium, and zirconium. The chemical formulas of compounds of tin, phosphorus, arsenic, and antimony in their anhydride form are as follows.

Boron compounds; LiBF ₄ Titanium compounds; LiTiF ₅ , Li ₂ TiF ₆ , Li ₃ TiF ₇ Zirconium compounds; LiZrF ₅ , Li ₂ ZrF ₆ ,
Li ₃ ZrF ₇ tin compound; LiSnF ₃ , Li ₂ SnF ₄ , LiSnF ₅ ,
Li ₂ SnF ₆ , Li ₄ SnF ₈ phosphorus compounds; LiPF ₄ , LiPF ₆ arsenic compounds; LiAsF ₄ , LiAsF ₆ antimony compounds; LiSbF ₄ , Li ₂ SbF ₅ , Li ₃ SbF ₆ ,
_{LiSb2F7 , Li2SbF5 , Li3S2F9 , LiSbF6 ,
Li2SbF7 , LiSb3F12 , Li2SbF13 , Li2Sb3F14 , _}
Li ₃ Sb ₄ F ₁₅ On the other hand, the high purity lithium fluoride complex salt targeted by the present invention is a compound represented by the following chemical formula.

LiBF ₄ , Li ₂ SiF ₆ , Li ₂ TiF ₆ , Li ₂ ZrF ₆ ,
Li ₂ GeF ₆ , LiSnF ₆ , LiPF ₆ , LiVF ₆ , LiAsF ₆ ,
LiNbF ₆ , LiSbF ₆ , LiTaF ₆ , LiBiF ₆ , Li ₂ VF ₇ ,
Comparing the chemical formulas of Li ₂ NbF ₇ , Li ₂ SbF ₇ , Li ₂ TaF ₇ , and Li ₂ BiF ₇ , the former contains lower-order fluorine compounds; Only higher fluorine compounds are shown in the latter chemical formula. Such lower fluorine compounds are often contained in crude lithium fluoride complex salts (crude complex salts) as impurities in higher fluorine compounds, together with the above-mentioned water and oxyfluorine compounds. However, the total amount of these impurities in the crude complex salt referred to in the present invention must be 10% by weight or less, and if the amount of impurities is abnormally greater than 10% by weight, the contact with fluorine referred to in the present invention The heat generated during this process makes it difficult to maintain a reaction temperature of -10 to +100°C, which not only poses operational danger, but also causes loss of fluorine, making it industrially unprofitable.

This reaction temperature of -10°C to +100°C is a temperature at which a high-purity product can be obtained without secondary decomposition of the above-mentioned target high-order fluorine compound using fluorine in an inert gas. In other words, at temperatures below -10℃, the fluorination reaction becomes extremely slow, making it virtually difficult to reduce impurities, and at temperatures above +100℃, some of the volatile components in the above and higher fluorine compounds dissipate. This tends to cause side reactions such as, and the purity of the product actually decreases. Regarding the reaction between impurities in the crude complex salt and fluorine, the following reactions occur collectively.

(1) The above-mentioned lower fluorine compound and fluorine undergo an addition reaction to increase the content of the higher fluorine compound.

(2) Metal oxyfluorides, metal oxides, and basic metal fluorides can be eliminated by fluorination reactions. For example, if M is a metal element, MOF,
Oxyfluorides such as MOF ₂ and MOF ₃ react as MOFn+2F ₂ →MFn ₊₂ +OF ₂ and the oxygen content decreases.

(3) Moisture (adhered water or crystallized water) can be removed by reacting with it as follows.

H ₂ O + 2F ₂ → 2HF + OF ₂ Oxygen fluoride is a low boiling point gas (OF ₂ is bp.-
145°C, O ₂ F ₂ bp.-57°C), which can be easily removed.

In the method of the present invention, when bringing the crude complex salt and fluorine into contact, it is necessary to control the reaction temperature between -10 and +100°C. It performs reactions between gases. Inert gases include helium, neon, argon, hydrogen fluoride, sulfur hexafluoride, carbon tetrafluoride, ethane hexafluoride, nitrogen trifluoride, nitrogen, oxygen difluoride, boron fluoride, and pentafluoride. Chlorine, etc.

In the method of the present invention, a solid-gas reaction is carried out under reduced pressure, normal pressure, or increased pressure, and the method is not only a simple flow method or a packing method, but also a fluidized bed method, a fluidized method, and a solid-gas reaction. This can be carried out using a mechanical stirring type reactor or a solid rotary stirring type reactor. The reaction operation according to the method of the present invention can be accomplished within a few seconds to several tens of hours if it is a batch reaction, depending on the amount and concentration of fluorine used, the type and nature of the inert gas, and the reaction conditions. After the reaction is completed, unreacted fluorine can be removed by passing an inert gas through the reaction system. The method described above can be carried out not only in a batch method but also in a continuous method, and the method of the present invention in which a solid-gas is brought into contact is particularly suitable for a continuous method.

As mentioned above, the high purity lithium fluoride complex salt purified by the method of the present invention is a highly purified lithium fluoride complex salt that is highly fluorinated.
All of their products come in the form of beautiful, free-flowing white crystals or powders. If this product is handled with sufficient care, the moisture in the product will disappear.
0.02% or less, especially 0.00001-0.01% in many cases
range, making it a versatile virtually anhydrous product. Moisture in products can be determined by mechanical analysis as well as the Karl-Futscher method. Furthermore, if the raw material crude complex salt is free of impurities introduced from containers and other handling equipment during the manufacturing process and is manufactured by normal synthetic methods, the purity of the target product is 99% or more, especially in many cases. teeth
99.5~100% lithium fluoride complex salt can be obtained.

Next, the technical content regarding the method of the present invention will be explained in more detail with reference to Examples.

It goes without saying that the method of the present invention can be carried out by arbitrarily changing its embodiments without departing from its spirit and spirit, and should not be interpreted as being limited to the following examples. Of course.

Example 1 345 g of lithium fluoride was placed in a container made of tetrafluoroethylene, and then 3000 g of hydrogen fluoride was added and dissolved. Boron trifluoride (BF ₃ ) gas is passed through this solution under slight pressure. After crystals of lithium borofluoride have sufficiently precipitated, the mixture is heated to distill off hydrogen fluoride. The obtained crude lithium borofluoride weighed 1200 g and contained 0.1% water. Put this in a rotary mixer,
After passing fluorine gas (F ₂ 10%) diluted with argon-nitrogen gas at a temperature of 30 to 50°C at 10/hr for 4 hours, dry nitrogen gas was further passed at 10/hr for 30 minutes to remove any unreacted gas. Drives out fluorine gas. The crystals are then ground in a stream of purified nitrogen and sealed in polytetrafluoroethylene bottles. The purity of the lithium borofluoride thus obtained was 99.83%, and it was a high purity product containing 5 ppm of water as an impurity.

Example 2 325 g of lithium hydroxide is added to 2000 g of a 65-70% hexafluorophosphoric acid solution prepared by the reaction of phosphoric anhydride and hydrogen fluoride while stirring under ice cooling. After stirring was continued for about 2 hours after the addition, the reaction mixture was filtered and the liquid was concentrated under reduced pressure to obtain a paste. When this paste-like material is transferred to a platinum plate and dried under high vacuum, crude lithium hexafluorophosphate (LiPF ₆ ) is produced as a white crystal mass at 1300%
~1400g was obtained. This substance is considered as an impurity.
It contained 0.1% LiPO ₂ F ₂ and 0.2% H ₂ O. This material was pulverized and put into a cylindrical stirring-mixing reactor, and fluorine gas (F ₂ 6%) diluted with argon was passed through it for 9 hours at a rate of 10 to 15 per hour.
Pass dry nitrogen gas through for 10 min to remove unreacted _F2 gas. The lithium hexafluorophosphate thus obtained was high purity lithium hexafluorophosphate containing 8 ppm of H ₂ O.

Example 3 If lithium hexafluoroarsenate hydrate (LiAsF ₆ 3H ₂ O) prepared by a conventional method from an aqueous hexalfluoroarsenic acid solution and lithium hydroxide is dried under reduced pressure at 50 to 70°C, the water content will be 0.1. % crude complex salt is obtained.
This crude complex salt was placed in a groove-type stirring reactor, and while stirring, fluorine gas (F ₂ 15%) diluted with helium was added.
When processed in the same manner as in Example 2 through
High purity lithium hexafluoroarsenate with H ₂ O of 20 ppm was obtained.

Example 4 An aqueous solution of lithium perchlorate or lithium borofluoride is added to an aqueous solution of a complex salt of antimony trifluoride and potassium fluoride (KSbF ₄ ) to cause double decomposition to produce an aqueous solution of lithium tetrafluoroantimonate, This was then concentrated under reduced pressure to obtain crude lithium tetrafluoroantimonate (LiSbF ₄ ).
Create. This product contained some basic salts and 0.2% water. 500 g of this material was placed in a rotary reactor and treated in the same manner as in Example 2. This treatment converts the antimony compound into lithium hexafluoroantimonate and removes water. The obtained lithium hexafluoroantimonate was used as LiSbF ₆
It had a purity of 99.81% _H2O 30ppm.

In this way, from lower fluorides to higher fluorides,
Furthermore, the method of the present invention can be conveniently applied to a method of simultaneously removing impurities and obtaining a highly purified lithium fluoride complex salt.

Claims (1)

[Claims] 1. A crude complex salt having a structure consisting of a fluoride of an element in groups 3 to 5 of the periodic table and lithium fluoride is brought into contact with fluorine gas at -10 to +100°C in an inert gas. A method for purifying lithium fluoride complex salt. 2 The fluoride of elements from groups 3 to 5 of the periodic table is boron,
The lithium fluoride according to claim 1, which is at least one fluoride selected from the group consisting of fluorides of silicon, titanium, germanium, zirconium, tin, phosphorus, vanadium, arsenic, niobium, antimony, tantalum, and bismuth. Method for purifying complex salts. 3. The inert gas is from the group consisting of hydrogen fluoride gas, helium, neon, argon, nitrogen, carbon tetrafluoride, sulfur hexafluoride, oxygen difluoride, boron fluoride, nitrogen trifluoride, and chlorine pentafluoride. The method for purifying a lithium fluoride complex salt according to claim 1, wherein at least one selected inert gas is used.