METHODS OF PRODUCING ALUMINUM FLUORIDE FROM CRYOLITE BATH

Abstract

New methods of producing aluminum fluoride from cryolite are disclosed. A method may include a step of reacting cryolite bath materials with aluminum sulfate, thereby producing a reactant product, the reactant product comprising aluminum fluoride. The method may further include a step of removing impurities from the reactant product, thereby creating a purified product comprising the aluminum fluoride. The removed impurities may comprise at least one of sodium (Na), magnesium (Mg), and calcium (Ca). In one embodiment, due to the removing step, the purified product contains not greater than 0.2 wt. % of calcium.

Claims

1. A method comprising: (a) reacting cryolite bath materials with aluminum sulfate, thereby producing a reactant product, wherein the reactant product comprises aluminum fluoride; and (b) removing impurities from the reactant product, thereby creating a purified product comprising the aluminum fluoride, wherein the impurities comprise at least one of sodium (Na), magnesium (Mg), and calcium (Ca), wherein, due to the removing step, the purified product contains not greater than 0.2 wt. % of calcium.

2. The method of claim 1, wherein the reacting comprises reacting at a temperature of from 400 to 600° C.

3. The method of claim 1, wherein the reacting comprises solid state reacting.

4. The method of claim 1, wherein the aluminum sulfate comprises anhydrous aluminum sulfate.

5. The method of claim 1, wherein the impurities comprise at least one sulfate.

6. The method of claim 5, wherein the at least one sulfate is at least one of sodium sulfate, magnesium sulfate and calcium sulfate.

7. The method of claim 1, comprising: prior to the reacting step, creating a precursor mixture, wherein the precursor mixture comprises the cryolite bath materials and the aluminum sulfate.

8. The method of claim 7, wherein the creating step comprises creating particles of the cryolite bath materials.

9. The method of claim 8, wherein the creating particles comprises at least one of grinding, crushing, and pulverizing of raw cryolite bath materials.

10. The method of claim 1, wherein the removing comprises washing the reactant product with an aqueous solution.

11. The method of claim 10, wherein the aqueous solution is water or deionized water.

12. The method of claim 10, wherein the washing comprises transferring at least one of sodium sulfate and magnesium sulfate from the reactant product to the aqueous solution.

13. The method of claim 10, wherein the washing is conducted at a temperature of not greater than 50° C., or not greater than 40° C., or not greater than 35° C., or not greater than 30° C.

14. The method of claim 1, wherein the impurities comprise calcium byproducts, and wherein the method comprises decomposing at least some of the calcium byproducts, thereby producing calcium oxide materials.

15. The method of claim 14, wherein the decomposing comprises heating the reactant product to a temperature of at least 800° C., or at least 850° C. or at least 900° C.

16. The method of claim 14, comprising, after the decomposing step, removing at least some of the calcium oxide materials from the reactant product.

17. The method of claim 16, wherein the removing calcium oxide materials step comprises exposing the decomposed reactant product to a chloride-containing solution.

18. The method of claim 1, comprising heat treating the reactant product to produce a heat treated product, wherein the heat treating comprises heating the reactant product to one or more temperatures within the range of 550-700° C.

19. The method of claim 18, comprising contacting the heat treated product with an acid thereby producing an acid-treated product.

20. The method of claim 19, comprising, prior to the contacting, creating an aqueous slurry comprising the heat treated product; wherein the contacting comprises adding the acid to the aqueous slurry.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a flow chart illustrating one embodiment of a method for producing a purified aluminum fluoride product in accordance with the present disclosure.

[0026] FIG. 2 is a flow chart illustrating embodiments of the reacting step (100) of FIG. 1.

[0027] FIGS. 3A-3B are flow chart illustrating different embodiments of the removing step (200) of FIG. 1.

[0028] FIG. 4 is a flow chart illustrating embodiments of an optional preparing step (50) useful with the embodiments of FIG. 1.

DETAILED DESCRIPTION

Example 1

[0029] Cryolite bath and anhydrous aluminum sulfate were mixed and then crushed/ground to 100 mesh. The materials were then heated to a temperature within the range of 500-600° C. for about 2.5 hours to facilitate their solid state reaction. After cooling to room temperature, the reactant products were ground, washed in water, filtered, and then dried by heating to about 110-120° C. The sodium, calcium and magnesium content of the reactant products is shown in Table 1, below, as measured by ICP.

[0030] Next, the dried products were heat treated a temperature within the range of 550-700° C. for about 2 hours and then cooled to room temperature. An aqueous slurry was then made using the heat treated products and water. HCl was added to the slurry until the pH was about 1.0-1.1. The acid treated materials were then washed and filtered and then dried by heating to about 110-120° C. The sodium, calcium and magnesium content of the final, purified product is shown in Table 1, below. As shown, the removal process removes all detectable amounts of calcium and magnesium and removes nearly all sodium.

TABLE-US-00001 TABLE 1 Impurity concentrations - Example 1 (wt. %)* Product Sodium Calcium Magnesium Rinsed Reactant Product 6.8 1.1 N.D. Final, Purified Product 0.34 N.D. N.D. *N.D. = below the analytic detection limit of 0.067 wt. % Ca or 0.055 wt. % Mg.

Example 2

[0031] Reactant products made from cryolite bath and anhydrous aluminum sulfate were prepared generally as per Example 1. After cooling to room temperature, the reactant products were ground, washed in water, filtered, and then dried by heating to about 110-120° C. The sodium, calcium and magnesium content of the reactant products is shown in Table 2, below.

[0032] This time, an aqueous slurry was made from the dried products and water, i.e., a heat treatment was not completed. HCl was added to the slurry until the pH was about 1.0-1.1. The acid treated materials were then washed and filtered and then dried by heating to about 110-120° C. The sodium, calcium and magnesium content of the final, purified product is shown in Table 2, below. As shown, the removal process removes all detectable amounts of calcium and magnesium and removes nearly all sodium. This process may be used, for instance, when the sodium concentration in the reactant materials is below average.

TABLE-US-00002 TABLE 1 Impurity concentrations - Example 2 (wt. %)* Product Sodium Calcium Magnesium Final, Purified Product 0.65 N.D. N.D. *N.D. = below the analytic detection limit of 0.067 wt. % Ca or 0.055 wt. % Mg.

[0033] While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. Further still, unless the context clearly requires otherwise, the various steps may be carried out in any desired order, and any applicable steps may be added and/or eliminated.