Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Alkali metal
Reexamination Certificate
2000-11-07
2002-12-24
Silverman, Stanley S. (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Alkali metal
C423S163000, C423S165000, C423S499300
Reexamination Certificate
active
06497850
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to an integral process that uses a minimum number of process steps for producing chemical and high purity grades of lithium carbonate and lithium chloride directly from the same natural brine source.
It is desirable, from a commercial standpoint, to provide a source of lithium low in sodium content because sodium becomes reactive and potentially explosive in certain chemical processes, particularly those in production of lithium metal from lithium salts. A substantial portion of presently available lithium is recovered from brines, which also contain high levels of sodium, making the production of low sodium lithium salts difficult and expensive. At the present time, there does not exist a viable low cost integral processes for producing low sodium lithium carbonate and chemical and high purity grades of lithium chloride directly from natural brines containing lithium.
Natural brines that contain lithium also contain many constituents as illustrated in the following Table:
TABLE 1
NATURAL BRINE COMPOSITION
Great
Bonne-
Salton
Silver
Dead
Salt
ville
Sea
Peak
Salar de Atacama
Sea
Lake
Brine
Brine
Brine
Brines
Ocean
Israel
Utah
Utah
Calif
Nevada
Chile
Na
1.05
3.0
7.0
9.4
5.71
6.2
7.17
5.70
K
0.038
0.6
0.4
0.6
1.42
0.8
1.85
1.71
Mg
0.123
4.0
0.8
0.4
0.028
0.02
0.96
1.37
Li
0.0001
0.002
0.006
0.007
0.022
0.02
0.15
0.193
Ca
0.04
0.05
1.5
0.5
0.0
0.71
1.46
0.043
Cl
1.9
16.0
14.0
16.0
15.06
10.06
16.04
17.07
Br
0.0065
0.4
0.0
0.0
0.0
0.002
0.005
0.005
B
0.0004
0.003
0.007
0.007
0.039
0.005
0.04
0.04
Li/Mg
0.0008
0.0005
0.0075
0.0175
0.786
1.0
0.156
0.141
Li/K
0.0026
0.0033
0.015
0.0049
0.0155
0.016
0.081
0.113
Li/Ca
0.0025
0.0064
0.2
0.0583
0.0008
1.0
4.84
0.244
Li/B
0.25
0.6666
0.857
1.0
0.051
4.0
3.75
4.83
(All values in weight percent)
Production of lithium carbonate and lithium chloride with acceptable qualities from such brines requires employing techniques to remove specific cations and anions that accompany the lithium in solution, and then concentrating the lithium for extraction.
Individual applications require that these ion impurities be reduced to specific maximum levels and a number of processes have been described for removing these impurities. For example, U.S. Pat. No. 5,219,550 to Brown and Boryta describes a method for producing chemical grade lithium carbonate from natural lithium containing brine by first removing most of the components from the brine by concentrating utilizing solar evaporation techniques. Concentrating the brine with respect to lithium by solar evaporation causes most of the unwanted components to precipitate from the brine, i.e., salt out. Boron, which concentrates with the lithium, is subsequently removed using an extraction process. The remaining magnesium is removed by adding a base to precipitate magnesium carbonate and/or magnesium hydroxide, and the lithium is finally precipitated from the purified brine as lithium carbonate by the addition of soda ash. Other processes related to the above process are disclosed in U.S. Pat. Nos. 4,036,718; 4,243,392; and 4,261,960.
Other techniques for producing purified lithium salts are known. For example, German Patent DE 19,541,558 to Wusson et al describes a process to reduce sodium from lithium chloride solutions by cooling. U.S. Pat. No. 4,859,343 to Kullberg et al describes an ion exchange method for removing sodium from brines. U.S. Pat. No. 5,599,516 and Russian Patent No. 9,419,280 describe absorption/ion exchange processes for recovering lithium from brine.
U.S. Pat. No. 4,980,136 discloses a procedure for preparing chemical grade and low sodium lithium chloride (battery grade, less than 20 ppm sodium and less than 5 ppm magnesium) from concentrated natural brine by crystallizing lithium chloride from a magnesium/lithium chloride brine to produce a chemical grade of lithium chloride crystal. This is followed by alcoholic extraction of the soluble lithium chloride from the crystal leaving sodium chloride as the insoluble phase. The alcohol solution containing the lithium chloride is then filtered and evaporated to form a high purity grade of lithium chloride crystal.
East German Patent DD 257,245 describes a method for recovering lithium chloride from concentrated brine containing both calcium chloride and magnesium chloride and selectively extracting lithium chloride with alcohol. Other patents related to such processes include U.S. Pat. Nos. 4,271,131 and 4,274,834.
U.S. Pat. No. 4,207,297 describes production of a low sodium lithium carbonate (sodium less than 10 ppm in lithium carbonate) from technical lithium carbonate. This is accomplished by reacting lithium carbonate with lime followed by filtration to produce a lithium hydroxide solution. The solution is subsequently purified with just enough carbon dioxide to remove the residual calcium and filtered. More carbon dioxide gas is added to the purified lithium hydroxide solution to re-precipitate lithium carbonate crystal as a high purity product.
Except for the methods described in DE 19,541,558, U.S. Pat. No. 4,243,392 and 5,219,550, the methods of the prior art are not practiced today because they are either technically or economically not viable.
Another process for producing lithium chloride is set forth in Chilean Patent Application No. 550-95, which describes a procedure whereby a purified brine containing essentially lithium chloride is directly produced from natural brines that have been concentrated by solar evaporation and treated by an extraction process to remove boron. However, the sodium, calcium, and sulfate levels in the resultant brine are too high to be an acceptable brine source of lithium chloride for producing a technical grade lithium metal, primarily because the two major remaining impurities, sodium and magnesium, have to be further reduced to acceptable levels to produce chemical grade lithium chloride crystal. Specifically, magnesium must be reduced to less than 0.005 wt % Mg, and sodium to less than 0.16 wt % Na in the anhydrous lithium chloride salt. Salting out anhydrous lithium chloride directly from brine above 110° C. in a vacuum crystallizer as described in U.S. Pat. No. 4,980,136 yields a lithium chloride containing at best 0.07 wt % Mg and 0.17 wt % Na.
It is accepted, although not proven, that lithium chloride crystal containing 0.07 wt % Mg may be too high in magnesium to be used for producing lithium metal and for subsequent use in the production of lithium organometallic compounds. Thus, the industry demands that organolithium catalysts in polymerization reactions be low in magnesium. Lithium chloride high in magnesium can also adversely affect the operation of the lithium electrolysis cell when producing the lithium metal.
As noted above, the sodium impurity in the lithium chloride crystal reports directly to the metal when producing lithium metal. Thus, low sodium lithium salts are desirable. Sodium in lithium chloride crystal above 0.6 wt % produces metal containing 1 wt % sodium or higher. Sodium concentrations of about 1 wt % in lithium metal or above renders the lithium metal more reactive to natural components of air. This makes the metal more difficult and more dangerous to handle. Table 2 sets forth data concerning sodium limits and tolerances in different lithium sources:
TABLE 2
Sodium Content of Lithium Chloride
Brown &
maximum limits for
Na in LiCl
Becherman
chemical grade
chloride required for
chemical grade
metal
battery grade metal
% Lithium
99.2
99.2
99.8
chloride
% Na**
0.17
0.04
0.0006
**wt % in Lithium chloride
Commercial methods employed to produce low sodium lithium carbonate and lithium chloride on a commercial scale include extraction of lithium compounds from mineral deposits such as spodumene bearing ore and natural brines. A number of processes have been described and some have been commercialized for producing lithium carbonate from these sources.
One such commercial method involves extraction of lithium from a lithium containing ore or brine to make a pure lithium sulfate solution such as described i
Boryta Daniel Alfred
Kullberg Teresita Frianeza
Thurston Anthony Michael
Chemetall Foote Corporation
Fulbright & Jaworski L.L.P.
Medina Maribel
Silverman Stanley S.
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