CS257729B1 - Process for producing lithium carbonate - Google Patents

Abstract

A method for producing lithium carbonate from an aqueous phase containing lithium hydroxide by converting lithium hydroxide by introducing gaseous carbon dioxide into the aqueous phase into a suspension of lithium carbonate and lithium bicarbonate. The bicarbonate is converted into lithium carbonate by heating to a temperature of 90 to 100°C. The suspended lithium carbonate is separated from the aqueous phase in the form of a powder by evaporation, settling, filtration or centrifugation.

Description

The present invention relates to a process for the production of lithium carbonate from an aqueous phase containing lithium hydroxide, in particular from an aqueous phase which is omitted during the manufacture of liquid rubbers by anionic solution polymerization initiated by lithium or its compounds, or omitted in the manufacture of this initiator. Lithium carbonate is particularly a raw material in the production of white enamel frits.

In the manufacture of liquid rubbers, e.g. liquid polybutadiene, anionic solution polymerization initiated by lithium or its compounds, such as aorganolithic initiators, results in the hydrolysis of the polymer and the lithium atoms at the chain ends with water or an aqueous acid solution. The aqueous phase is then separated from the polymer solution. The preparation of these polymers is described, for example, in U.S. Pat. Nos. 1,301,521, VB 1,004,723, U.S. Pat. No. 3,225,089 and U.S. Pat. No. 3,135,716, and U.S. Pat. No. 829,635.

It is therefore an object of the invention to find an economically advantageous method of use for aqueous lithium hydroxide solutions, while avoiding the environmental waste associated with its discharge into water or the cost of purification.

These disadvantages are overcome by the process for producing lithium carbonate from the aqueous phase containing lithium hydroxide, in particular from the aqueous phase which is lost in the manufacture of liquid rubbers by anionic solution polymerization initiated by lithium or its compounds or in the manufacture of this initiator according to the invention. The lithium contained in the aqueous phase converts under stirring at a pressure of 0.1 to 0.3 MPa by introducing gaseous carbon dioxide into the aqueous phase to suppress lithium carbonate and lithium bicarbonate, then decomposing the acidic carbonate by heating the suspension to a temperature of 90 to 100 ° C. lithium to lithium carbonate, and then the suspended lithium carbonate is separated from the aqueous phase in the form of a powder by evaporating, filtering, separating or centrifuging. ,

Advantageously, the process according to the invention can be carried out by distilling off organic solvents from the aqueous phase prior to the introduction of carbon dioxide and mechanically separating the cross-linked polymer gel present. This mechanical separation can be carried out, in particular, by filtration or sedimentation. Solvents which are distilled off include, in particular, an ether such as methyl tert-butyl ether or an alcohol such as methanol or tertiary butanol.

The process according to the invention can also advantageously be carried out by heating the slurry with the heat of reaction resulting from the reaction of lithium hydroxide with carbon dioxide. The slurry is preferably heated to a temperature of 90 to 95 ° C, which is optimal for decomposing the acid carbonate to lithium carbonate. The heating may preferably be carried out for a period of at least 1 hour to ensure complete decomposition to lithium carbonate.

The separation of the suspended lithium carbonate from the aqueous phase in the form of a powder can advantageously be effected by separating the solid particles, in particular by vacuum filtration or centrifugation, followed by air drying at 100 to 150 ° C.

The separation of the suspended lithium carbonate from the aqueous phase in the form of a powder is advantageous to be carried out at a temperature of 890 to 100 ° C because its solubility decreases with increasing temperature.

An advantage of the process according to the invention is that the aqueous lithium hydroxide solution is used for the production of a reusable product, at the same time avoiding environmental impacts associated with its discharge into water or cleaning costs.

The advantages of the process according to the invention are further illustrated by the following examples. of a particular embodiment.

Example 1

150 l of the aqueous phase obtained in the production of liquid polybutadiene with a content of 4 wt. % lithium hydroxide and 0.2 wt. of methyl tert-butyl ether was heated in a distillation column digester to 60 ° C. After the methyl tert-butyl ether was distilled off, the aqueous lithium hydroxide solution from the distillation column boil was transferred to a reactor where 5.6 kg of carbon dioxide gas were introduced with stirring. The mother liquor, with suspended lithium carbonate powder, was heated to about 95 ° C by reaction heat and maintained at this temperature for 1 h. After this time, the lithium carbonate was hot filtered from the mother liquor under vacuum. The wet lithium carbonate was spread over a hot air oven tray in which it was dried at 130 ° C for 2 hours. This gave 7.5 kg of lithium carbonate powder.

Example 2

Of the 150 L water phase obtained in the production of liquid polybutadiene with hydroxyl end groups, containing 5.8 wt. lithium hydroxide, 0.72 wt. % methyl tert-butyl ether, 14.45 wt. of methanol, a methyl tert-butyl ether, methanol and a small amount of water were distilled off in the distillation column digester. 0.3 kg of sludge was separated from the digester liquid by filtration on a nylon mesh. Pure aqueous lithium hydroxide solution was charged to the reactor, where 4 kg of carbon dioxide gas was fed under stirring at 40 psi at 40 psi. By reaction heat, the lithium carbonate slurry with mother liquor is heated up to about 95 ° C and kept at this temperature with stirring for 1 hour. After this time, the lithium carbonate powder was separated in the centrifuge while hot. The wet product was spread on a hot-air oven tray in which it was dried at 130 ° C for 2 h. 9.8 kg of lithium carbonate was obtained.

Example3

150 l of the aqueous phase obtained after the disposal of lithium in the initiator reactor containing 10.51 wt. % lithium hydroxide, 0.1 wt. of methyl tert-butyl ether, 0.05 wt. % methanol and 0.05 wt. tert-butanol, was heated to 101 ° C in the distillation column digester to distill the organic solvents.

The evaporation liquid containing the aqueous lithium hydroxide solution was interrupted into the reactor, where 15 kg of carbon dioxide gas was added at 40 ° C with stirring at 0.3 MPa.

The mother liquor with suspended lithium carbonate powder was heated up to about 95 ° C and held at this temperature for 1 hour with stirring. After this time, the lithium carbonate was hot filtered from the mother liquor under vacuum. The wet product was spread over foxes in a hot air oven in which it was dried at 130 ° C for 2 hours. This gave 21.6 kg of lithium carbonate.

Claims (8)

OBJECT OF THE INVENTION A process for producing lithium carbonate from a lithium hydroxide-containing aqueous phase, in particular a phase which is lost in the manufacture of liquid rubbers by anionic solution polymerization initiated by lithium or its compounds, or which is lost in the manufacture of this initiator, characterized in that with stirring at a pressure of 0.1 to 0.3 MPa by introducing gaseous carbon dioxide into the aqueous phase into a slurry of lithium carbonate and acidic lithium carbonate, then decomposing the lithium acidic carbonate to lithium carbonate by heating the slurry to 90-100 ° C. this suspended lithium carbonate separates from the aqueous phase in the form of a powder by scalding, filtering, separating or centrifuging. 2. The process of claim 1 wherein organic solvents are distilled off from the aqueous phase prior to the introduction of carbon dioxide and the present crosslinked polymer sludge is mechanically separated. 3. The process according to claim 1, wherein the heating of the slurry with the aqueous phase is carried out by the reaction heat generated by the reaction of lithium hydroxide with carbon dioxide. 4. A process according to any one of claims 1 to 3, wherein the suspension is heated to a temperature of 90 to 95 ° C. 5. A process according to any one of claims 1-4, characterized in that the decomposition of the acid carbonate to lithium carbonate is carried out by heating the suspension for at least 1 hour. 6. A process according to any one of Claims 1 to 5, characterized in that the separation of the suspended lithium carbonate from the aqueous phase in the form of a powder is carried out by separating the solid particles followed by air drying at 100 to 150 ° C. 7. A process according to any one of claims 1 to 6, wherein the separation of the suspended lithium carbonate from the aqueous phase in the form of a powder is carried out by vacuum filtration or centrifugation. 8. A process according to any one of claims 1 to 7, wherein the suspended lithium carbonate is separated from the aqueous phase in the form of a powder at a temperature of 90 to 100 ° C.