Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Alkali metal
Reexamination Certificate
2001-04-02
2003-11-25
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Alkali metal
C423S208000, C423S395000, C423S499100, C423S551000, C423S642000, C423S421000, C423S499300, C423S499400, C562S579000, C562S582000, C562S584000, C562S585000, C562S589000, C562S590000, C562S597000, C562S598000, C562S601000, C562S606000, C562S607000, C562S609000
Reexamination Certificate
active
06652820
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to cesium salts and other alkali metal salts and methods of making the same.
Cesium salts, such as cesium formate, are increasingly being discovered as useful additives for a variety of industrial applications such as in the hydrocarbon recovery areas. Accordingly, there is a desire to develop processes which produce relatively high purity cesium salts efficiently and economically.
Previously, barium hydroxide and soluble barium salts have been used as reactants with cesium sulfate solutions in the formation of cesium salts. However, barium compounds are very expensive reactants and therefore undesirable.
Other processes have attempted to avoid the use of barium compounds and use cesium-aluminum-alum which is reacted in the presence of water with calcium hydroxide and a water soluble calcium salt. However, such a process requires the use of a soluble acid salt of lime, like calcium formate, and doesn't address the removal of many impurities that exist in the cesium salt solution that is formed. There is also the very real risk of having soluble calcium salt contamination in the resultant product if the exact stoichiometric amount required is only slightly exceeded.
Accordingly, there is a need to develop improved processes for making cesium salts and other alkali metal salts which avoid one or more of the above-described disadvantages.
SUMMARY OF THE PRESENT INVENTION
A feature of the present invention is to provide a method of making cesium salt and other alkali metal salts which avoids the exclusive use of expensive barium compounds.
Another feature of the present invention is to provide a method of making cesium salt which uses cesium sulfate as one of the starting reactants.
An additional feature of the present invention is to provide a process which forms relatively high purity cesium salts without large amounts of impurities.
Additional features and advantages of the present invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims.
To achieve these and other advantages, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to a methods of making a cesium salt. In the methods, a cesium sulfate containing solution is reacted with lime to form a solution containing at least cesium hydroxide; and also formed is a residue containing calcium sulfate. The residue is then removed from the solution. The cesium hydroxide in the solution is then converted to at least one cesium salt. These steps can be repeated one or more times with the solution resulting in the last step in order to convert any remaining cesium sulfate, if desired, that remains in the solution.
The present invention further relates to a method of making cesium formate. In this method, a cesium sulfate containing solution is reacted with lime to form a solution containing cesium hydroxide and a residue containing calcium sulfate is also formed. The residue is removed from the solution. Afterwards, the cesium hydroxide in the solution is converted to cesium formate by the introduction of formic acid.
Furthermore, the present invention relates to a method of making cesium hydroxide which involves reacting a cesium sulfate containing solution with lime to form a solution containing at least cesium hydroxide and a residue containing calcium sulfate is also formed. The residue is then removed from the solution containing the cesium hydroxide.
Also, the present invention relates to a method of making an alkali metal salt comprising: a) reacting an alkali metal sulfate containing solution with lime to form 1) a solution comprising at least alkali metal hydroxide and 2) a residue comprising calcium sulfate; b) removing the residue from the solution; and c) converting the alkali metal sulfate hydroxide in the solution to at least one type of alkali metal salt.
In addition, the present invention relates to a method of making alkali metal hydroxide comprising: a) reacting an alkali metal sulfate containing solution with lime to form 1) a solution comprising at least alkali metal hydroxide and 2) a residue comprising calcium sulfate; and b) removing the residue from the solution.
The present invention also relates to a method of purifying alkali metal sulfate comprising: a) reacting an alkali metal sulfate containing solution with lime to form 1) a solution comprising at least alkali metal hydroxide and 2) a residue comprising calcium sulfate; b) removing the residue from the solution; and c) converting the alkali metal hydroxide in the solution to alkali metal sulfate, wherein the alkali metal sulfate in step c) has a purity higher than the alkali metal sulfate in step a).
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to a method of making a cesium salt and further relates to a method of making cesium hydroxide. The present invention, in addition, relates to methods of making alkali metal salts and alkali metal hydroxides.
In the preferred method of making cesium salts, a cesium sulfate containing solution is reacted with lime to form a solution comprising at least cesium hydroxide. A residue comprising calcium sulfate is also formed in the reaction, which is typically in the form of a precipitate. The residue comprising calcium sulfate is then removed from the solution and the cesium hydroxide in the solution is converted to at least one cesium salt.
The reacting of the cesium sulfate containing solution with the lime can occur at essentially any temperature and preferably occurs at a temperature of from about 0° C. to about 100° C., and more preferably occurs at a temperature of from about 0° C. to about 50° C., and even more preferably occurs at a temperature of from about 0° C. to about 30° C. Lower reaction temperatures are preferred in the present invention since the solubility of lime is significantly higher at lower temperatures. For instance, the lime solubility in the cesium sulfate containing solution is twice as high at about 20° C. to about 25° C. as compared to the lime solubility at 95° C.
The cesium sulfate containing solution or slurry is typically an aqueous solution which contains any soluble amount of cesium sulfate in solution. For purposes of the present invention, suspended solids can be present in the solution. For instance, from about 0 ppm to about 3000 ppm of suspended solids can be present in the solution. Preferably, the suspended solids are not potentially soluble calcium salts. Thus, for purposes of the present invention, the cesium sulfate containing solution can also be considered a slurry. Preferably, from about 1% to about 50% by weight of cesium sulfate is present in the cesium sulfate containing solution, and more preferably from about 1% to about 10% by weight, and even more preferably about 5% by weight cesium sulfate in the cesium sulfate containing solution. The cesium sulfate can be obtained from a variety of sources including, but not limited to, filtration of neutralized cesium alum derived from pollucite ore digestions, filtration of neutralized cesium alums intentionally formed when recycling various cesium salt scraps, reprocessing to cesium sulfate salt from spent catalysts, and the like. Extremely pure or impure cesium sulfate solutions can be converted to the desired cesium salt.
The lime used to react with the cesium sulfate containing solution can be any type of lime and is preferably a calcium oxide or is a calcium hydroxide (also known as a hydrated lime). If calcium
Bos Steven
Cabot Corporation
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