A process for preparing high-purity alkali metal hexafluorophosphate and the alkali metal hexafluorophosphate prepared therefrom

A process of preparing an ultra-high purity alkali metal hexafluorophosphate (MPF6), comprising following steps:

• a. charging alkali metal fluoride (MF) in a first reactor ‘B’ and flushing nitrogen gas through the same,
• b. cooling the first reactor ‘B’ to a predetermined temperature, followed by charging anhydrous hydrogen fluoride (AHF) gas and stirring the mixture comprising alkali metal fluoride (MF) dissolved in AHF in the first reactor ‘B’,
• c. cooling the mixture comprising alkali metal fluoride (MF) dissolved in AHF in the first reactor ‘B’ to a predetermined temperature,
• d. charging phosphorous pentachloride (PCl5) in a second reactor ‘A’ and adding AHF in multiple lots, to produce high purity phosphorous pentafluoride (PF5) and hydrogen chloride (HCl) gas,
• e. reacting alkali metal fluoride (MF) dissolved in AHF in the first reactor ‘B’ with phosphorus pentafluoride (PF5) and hydrogen chloride (HCl) gas mixture obtained in step (d) to obtain alkali metal hexafluorophosphate mother liquor dissolved in AHF under PF5 gas blanketing,
• f. cooling the first reactor ‘B’ to a predetermined temperature and maintaining the temperature of alkali metal hexafluorophosphate mother liquor dissolved in AHF for predetermined time, followed by filtration and drying at predetermined temperature to achieve alkali metal hexafluorophosphate (MPF6),
• g. obtaining the dried solid MPF6,
• wherein alkali metal ‘M’ is selected from Na, K and Cs and alkali metal hexafluorophosphate is selected from NaPF6, KPF6 or CsPF6.