Process for the preparation of lithium metaphosphate

Details Process for the preparation of lithium metaphosphate Process for the preparation of lithium metaphosphate

2002-03-29

2003-12-02

Silverman, Stanley S. (Department: 1754)

Chemistry of inorganic compounds

Phosphorus or compound thereof

Oxygen containing

Reexamination Certificate

active

06656441

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a novel process for the preparation of lithium metaphosphate (LiPO
3
) by a solid state thermal reaction. This compound is useful as an intermediate for the preparation of lithium hexa fluorophosphates (LiPF
6
). This salt is a good electrolyte in aqueous, non-aqueous, solid and selected polymer medium. The present invention particularly relates to the preparation of lithium metaphosphate (LiPO
3
) compound which is the basic chemical for the preparation of lithium hexafluorophosphates (LiPF
6
) by a novel solid state method which is not hitherto attempted anywhere.
BACKGROUND OF THE INVENTION
Prior art literature on lithium metaphosphate (LiPO
3
) discloses the reaction of lithium salts with metaphosphoric acid, which is obtained by heating pyro-phosphoric acid or ortho-phosphoric acid. The reaction occurring for the above two thermal processes are as follows:
1.
H
4
P
2
O
7
→
2HPO
3
+ H
2
O
2.
H
3
PO
3
→
HPO
3
+ H
2
O
HPO
3
+ LiOH
→
LiPO
3
+ H
2
O
REFERENCE
Advanced Inorganic Chemistry, S. Sathiya Prakash G. D. Tuli, S. K. Basu and R. D. Radan, S. Chand & Co., New Delhi, p. 988 (1998).
The above methods need controlled conditions for the preparation of lithium metaphosphate. The above methods for the preparation of lithium metaphosphate also suffer from the following disadvantages:
1. More than one step is involved to prepare LiPO
3
.
2. Needs crystallization procedure once the product is formed from aqueous solution.
OBJECTS OF THE INVENTION
The main object of this present invention is to provide a simple novel process for the synthesis of lithium meta phosphate (LiPO
3
) which obviates the draw back mentioned above.
Another object of the present invention is to provide a complete solid state reaction procedure for the preparation of LiPO
3
.
Another object of the invention is to provide a single step process to obtain LiPO
3
.
Yet another object of the invention is to get high yield of the product LiPO
3
(>90%).
SUMMARY OF THE INVENTION
The above and other objects have been achieved by the solid state method for the preparation of lithium metaphosphate of the invention.
Accordingly, the present invention provides a process for the preparation of lithium metaphosphate comprising reacting a lithium source and a phosphorous source in a ratio of 1:1-2 in solid state at a temperature in the range of 300 to 650° C. to obtain the desired lithium metaphosphate.
In one embodiment of the invention, the lithium source is selected from the group consisting of Li
2
O, LiCO
3
, LiOH, LiNO
3
and any mixture thereof.
In another embodiment of the invention, the phosphorous source is selected from the group consisting of ammonium pyrophosphate, ammonium orthophosphate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate and any mixture thereof.
In another embodiment of the invention, the reaction is carried out in solid state in a single step.
In yet another embodiment of the invention, the reaction is carried out at a temperature of 350° C. for a time period of 12 hours and the lithium source is selected from Li
2
O, LiOH and LiNO
3
.
In another embodiment of the invention, the reactive materials are heated in a muffle or in an electric furnace.
In yet another embodiment of the invention, Li
2
CO
3
is reacted with the phosphorous source at a temperature of 600° C.
In another embodiment the lithium source and the phosphorous source are mixed and ground well before being heated.
In another embodiment of the invention, the lithium source and the phosphorous source are mixed in an equimolar ratio.


REFERENCES:
patent: 3314750 (1967-04-01), Chung
patent: 0 306 205 (1989-03-01), None
patent: 1012410 (1965-12-01), None
R.C. Mehrotra and C.K. Oza: “Studies In Condensed Phosphates: Part IX-Complex Lithium Polymethaphosphate Derivatives Of Some Bivalent Metal Ions”, Indian Journal of Chemistry, vol. 6, Mar. 1968, pp. 158-160, XP-008011283.
Mehrotra, R.C. et al: “Complex Polymetaphosphates of Strongly Electropositive Elements”, Journal of the Indian Chemical Society, vol. 59, No. 4, Apr. 1982, pp. 486-492, XP-008011302.
Fokina, M.F. et al, Database Abstract Online: “Lithium metaphosphate”, database accession No. 78:143256 CA, XP-002222967.

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