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US 5,935,541 AGranted
Process for manufacture of lithium hexafluorophosphate
AssigneeElf Atochem S.A.
InventorsPhilippe Bonnet, Sylvain Perdrieux, Steven G. Schon
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AssigneeElf Atochem S.A.
InventorsPhilippe Bonnet, Sylvain Perdrieux, Steven G. Schon
Estimating the term…
The process of the present invention consists in bringing into contact, on the one hand, (A) gaseous phosphorus pentafluoride or a gaseous mixture comprising phosphorus pentafluoride and hydrochloric acid, and, on the other hand, (B) a solution of lithium fluoride in hydrofluoric acid, in a column (10) having a sufficient number of transfer units to carry out the reaction of PF.sub.5 with LiF under the chosen conditions of temperature, of pressure and of molar ratio of the two contrasting reactants and with complete or substantially complete absorption of the PF.sub.5 in the column. This process makes it possible to solve the problems of blockage by preventing recrystallizations of salts; to discharge the heat given off by the reaction by the evaporation of a portion of the HF; and to separate the HCl which may be contained in the starting PF.sub.5, without loss of PF.sub.5, thus allowing subsequent recovery/value enhancement of this HCl. Moreover, this process is very simple, with a very small number of stages, which makes it possible to avoid any entry of air or moisture capable of contaminating the final LiPF.sub.6.
Process for the manufacture of lithium hexafluorophosphate by reaction of phosphorus pentafluoride with lithium fluoride, comprising, on the one hand, (A) gaseous phosphorus pentafluoride or a gaseous mixture comprising phosphorus pentafluoride and hydrochloric acid and, on the other hand, (B) a solution of lithium fluoride in hydrofluoric acid are brought into contact in a column having a sufficient number of transfer units to carry out the reaction of phosphorus pentafluoride with lithium fluoride under predetermined conditions of temperature, of pressure and of molar ratio of the two contrasting reactants and with complete or substantially complete absorption of the phosphorus pentafluoride in the column wherein the content of lithium fluoride in its solution in the feed hydrofluoric acid (B) is selected so that the concentration of hydrofluoric acid is above the solubility threshold of the lithium fluoride and lithium hexafluorophosphate salts, taking into account also evaporation of a fraction of the hydrofluoric acid by energy given off by the reaction.
Dependencies are inferred from the claim text.