JPH0575694B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high temperature, two-step process for the production of lithium oxide of greater than 99% purity from low purity (85-95%) lithium peroxide.

<Prior Art> Lithium oxide typically contains impurities derived from the raw materials for producing lithium oxide. Lithium oxide typically contains small amounts of lithium hydroxide or lithium carbonate. The main end uses of lithium oxide are pharmaceuticals, lithium battery manufacturing and thermonuclear fusion reactors. However, in thermonuclear fusion reactions, high purity lithium oxide is desirable because the impurities, lithium hydroxide and lithium carbonate, melt at too low a temperature. In lithium battery applications, lithium hydroxide and lithium carbonate impurities are insoluble in the organic solvents used to manufacture lithium batteries.

A method for producing lithium oxide from lithium peroxide is disclosed by ROBach in US Pat. No. 3,321,277. This method is carried out slowly at 225 to 250°C in an inert atmosphere, preferably from 1 to 5 mm.
Lithium peroxide is decomposed into lithium oxide by heating under Hg vacuum for up to 24 hours.

U.S. Patent No. 2424512 awarded to RAStauffer
No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, 2003, 2003, 2006, 2003, 2003, discloses a method for the recovery of lithium oxide from silicate or phosphate ores. In this method, ore is pelletized with lime, and the pellets are heated to a temperature of over 900° C. under reduced pressure of less than 1 mmHg to cause displacement of lime and lithium oxide. The oxide is distilled out and condensed.

Inorganic Synthesis by AJCohen, No. 5
Volume, Chapter 1A, pp. 3-4, McGraw-Hill, New
York (1957) estimated that anhydrous lithium hydroxide
reported a method for producing lithium oxide by heating to 1/2 h under vacuum at 100°C.

US Pat. No. 4,221,775 to James A. Anno and Howard H. Bowing discloses the production of porous lithium oxide from lithium hydroxide having a purity of at least 97%. Anhydrous sodium hydroxide is produced by heating the lithium hydroxide monohydrate starting material to its melting point to drive off the water of crystallization. Continuous heating of anhydrous sodium hydroxide above its melting point was then carried out in an inert atmosphere while suppressing conversion of lithium hydroxide to lithium oxide. The dissolved anhydrous lithium hydroxide was then heated to 150 ml while protected in an inert atmosphere.
It was cooled to a temperature below °C. The cooled lithium hydroxide is then placed at a pressure of less than 2 μm Hg, preferably less than 1 μm Hg, at 150 to about 200° C. and maintained at that temperature until complete conversion to lithium oxide has occurred. The purity of the product was 98.1%.

The continuing need for practical processes for producing high-purity Li ₂ O has led to a number of lithium oxide production methods. Although higher purity lithium oxide is desired in the battery and fusion industries, lithium oxide with a purity of 99% or higher is not available.

<Structure of the Invention> The present invention decomposes impure lithium peroxide into impure lithium oxide at 350 to 450°C in an inert atmosphere substantially free of water, and then decomposes impure lithium oxide to impure lithium oxide at about 900°C. High-purity lithium oxide characterized by producing lithium oxide with a purity of 99% or more by heating it under vacuum to a temperature below the melting point of lithium oxide.
Provides a two-step process for the production of 99% or higher lithium oxide.

A key feature of this process is the elimination of active oxygen and moisture during the low temperature heating in step 1 of the process. This reduces corrosion of the crucible material, product degradation and sintering; it also reduces the sample placed into the crucible by approximately 90 to 95% containing only minor lithium hydroxide and lithium carbonate impurities.
of lithium oxide to ensure a higher assay material.
With reduced impurities, crucible corrosion and acid sintering are reduced or eliminated at high temperatures. Under the process conditions of the present invention, the product is friable and can be easily removed from the container.
Obtained as a non-sintered powder.

<Details of Embodiments> The first step of the method of the present invention is to decompose 85% to 95% pure lithium peroxide at a temperature of 350 to about 450°C to contain residual amounts of lithium carbonate and lithium hydroxide as impurities. This produces impure lithium oxide. Lithium hydroxide melts at around 450℃,
Avoid temperatures above 450°C to sinter the product. Temperatures lower than 350°C are not used because lithium peroxide decomposes very slowly at temperatures lower than 350°C.

In step 1 the lithium peroxide is placed under an inert atmosphere such as argon, nitrogen, helium, neon or krypton on stainless steel, aluminum, nickel or thermal glass or other materials that are inert towards lithium compounds at elevated temperatures. The material may be heated in an inert container. It is important to exclude water from the process. Excluding oxygen is helpful but not necessary.

The lithium oxide product from the first step contains significant amounts of lithium carbonate and lithium hydroxide, up to 20% or more as these contaminants, at about 900° C. or under moderate vacuum. Furthermore, it is preferably heated in a crucible, which may be a vibrating or rotating crucible, a crucible vibrated with ultrasonic energy or a crucible with some rotating or stirring means. Useful crucibles are made of alumina, magnesia, graphite, metal or metal with a high temperature inert film or coating. Temperatures below about 900°C can also be used, but will produce lithium oxide of lower purity. Higher temperatures below the melting point of lithium oxide can be used and result in a finely divided product. Temperatures above 1000°C are not necessary to produce the desired products of this invention; therefore, heating of about 900 to 1000°C is sufficient and preferred. Heating to 1200°C to 1300°C can also be used, but such high temperatures will excessively increase lithium oxide product crucible erosion.

The second step of the method of the invention is carried out under moderate vacuum. A moderate vacuum (degrees) is necessary to exclude oxygen and to help remove small amounts of lithium carbonate and/or lithium hydroxide decomposition products from which the lithium peroxide feedstock for the first step was produced. A vacuum (degrees) created by a commercially available vacuum furnace capable of generating a vacuum of about 0.2 kPa or less is sufficient. The preferred vacuum (degrees) is approximately
It is in the range of 0.1kPa or less.

Lithium carbonate and lithium hydroxide are 800 to
It decomposes at temperatures in the range of 1000°C to produce lithium oxide and water or lithium oxide and carbon dioxide. This conversion reaction can be partially accomplished at 900° C. or above at normal pressure in an inert atmosphere, but can proceed completely under vacuum at 900° C. or above. At temperatures higher than 1000°C, the erosion by lithium compounds in the crucible is greater than at lower temperatures. Avoid crucible erosion as it is undesirable to have crucible material in the lithium oxide product.

Surprisingly from the point of view of the prior art, the method of the present invention for producing high purity lithium oxide uses process conditions that do not require exotic or special equipment or exceptional operating conditions, and achieves processes hitherto inaccessible. Produce lithium oxide with purity.

The following examples further illustrate the invention.

Example 1 A dry 90% lithium peroxide sample containing 8% lithium hydroxide and 2% lithium carbonate.
450°C was placed in an aluminum container. The sample was then heated for 2 hours at 425°C under argon, anhydrous, and non-oxidizing conditions.
heated for an hour. Product of first stage heating, containing 12% lithium hydroxide and 3% lithium carbonate
300g of 85% lithium oxide was placed in a high purity (99%) alumina crucible and heated to 950℃ under a vacuum of approximately 0.1kPa.
heated for an hour. Product (270g) was analyzed and found to be 99.97%
It turned out to be lithium oxide. The product was mostly a fine powder with only a few product globules.

Comparative Example A Example 1 was repeated using a heating temperature of 850°C during the second stage of heating under vacuum. The purity of the lithium oxide product was 97%.

Comparative Example B Example 1 was repeated without using vacuum during the second stage of heating to 950°C and heating under argon. The purity of lithium oxide was 95%.

Comparative Example C Single heating at 900° C. under vacuum and under argon was attempted separately. However, the decomposition of the lithium peroxide was so active that both the products and reactants violently spewed out of the crucible.

Claims (1)

[Claims] 1. (a) Lithium peroxide is decomposed at a temperature of 350 to 450° C. in an inert, anhydrous atmosphere to form impure lithium oxide; and (b) impure lithium oxide is decomposed. 99 by heating to 900℃ or higher for at least 1 hour under a pressure of 0.2kPa or lower.
A method for producing high-purity lithium oxide, characterized by obtaining high-purity lithium oxide with a purity of % or higher. 2. Transfer the impure lithium oxide from step (a) to step (b).
The method according to claim 1, wherein the material is heated to a temperature of 900° C. to 1000° C. under vacuum. 3 Impure lithium oxide from step (a) is processed in step (b).
The method according to claim 2, wherein the heating is performed under a pressure of 0.1 kPa or less. 4 Impure lithium oxide from step (a) is processed in step (b).
Claim 3 heating under a pressure of 0.1kPa
The method described in section.