ELECTROLYTIC PRODUCTION OF NITROGEN TRIFLUORIDE FROM A MOLTEN CSF-HF-NH4F SYSTEM

In order to decrease the vapor pressure of hydrogen fluoride (HF) and corrosion of the nickel anode in an electrolytic cell for the production of nitrogen trifluoride, the electrochemical behavior of nickel was investigated in the temperature range of 50-100-degrees-C using a molten CsF-HF-NH4F system. Anodic reaction on nickel seemed to vary with increasing potential, permitting division into four regions as follows: anodic dissolution of nickel in Region I (0-1 V vs. H-2), deposition of a Ni(II) compound on nickel in Region II (1-3 V), oxidation of Ni(II) film to Ni(III) and/or Ni(IV) compounds in Region III (3-5 V), and electrochemical fluorination of NH3 in Region IV (more positive than 5 V). The addition of CsF to the molten electrolyte reduces the corrosion of the nickel anode and reduces the vapor pressure of HF in the melt. A maximum current efficiency for NF3 formation was recorded at 100-degrees-C.